Light recycling directional control element and light emitting device using the same

ABSTRACT

In one embodiment of this invention, an optical element comprises a light recycling directional control element and provides increased spatial color or luminance uniformity, desired angular color uniformity, and customizable light re-direction properties. In one embodiment, the optical element comprises at least one light blocking region and a lenticular lens element. Further embodiments incorporate an anisotropic light backscattering region within a light transmitting layer. The optical element may further comprise a light collimating element or an additional light lenticular lens element and light transmitting region that may be oriented parallel or perpendicular to the first lenticular lens element. Light emitting devices and displays incorporating the light recycling direction control element are further embodiments of this invention.

RELATED APPLICATIONS

This applications claims the benefit of U.S. Provisional Application No.61/036,062, filed on Mar. 12, 2008, the entire contents are incorporatedherein by reference.

FIELD OF THE INVENTION

This invention generally relates to optical elements for recycling andspatial and angular control of light and using these elements in a lightemitting device such as a light fixture, backlight, display sign tocontrol at least one of properties of light output profile, viewingangles, uniformity, form factor, and efficiency.

BACKGROUND OF THE INVENTION

Light collimating films can be used in backlights for displays or signsto collimate the light and increase uniformity through total internalreflections. Traditional prismatic collimation films have limitations ontheir ability to highly collimate the incident light. Current methodsfor improving the uniformity of light in a backlight often involveexcess diffusion, light absorption and generally the thickness of thebacklight is increased or the mixing distance is substantially high.

SUMMARY OF THE INVENTION

In one embodiment of this invention, an optical element comprises alight recycling directional control element and provides increasedspatial color or luminance uniformity, desired angular color uniformity,and customizable light re-direction properties. In one embodiment, theoptical element comprises at least one light blocking region and alenticular lens element. Further embodiments incorporate an anisotropiclight backscattering region within a light transmitting layer. Theoptical element may further comprise a light collimating element or anadditional light lenticular lens element and light transmitting regionthat may be oriented parallel or perpendicular to the first lenticularlens element. Light emitting devices and displays incorporating thelight recycling direction control element are further embodiments ofthis invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a light recycling directional controlelement of one embodiment of this invention comprising a lightreflecting region.

FIG. 2 is a perspective view of a light recycling directional controlelement of one embodiment of this invention comprising a lenticular lensarray, light transmitting regions, and light absorbing regions.

FIG. 3 is a perspective view of a light recycling directional controlelement of one embodiment of this invention comprising a lenticular lensarray, light transmitting regions light absorbing regions and lightreflecting regions.

FIG. 4 is a perspective view of a light recycling directional controlelement of one embodiment of this invention comprising a lenticular lensarray, light transmitting regions, light absorbing regions and lightreflecting regions and an anisotropic light scattering region disposedin the substrate of the lenticular lens array.

FIG. 5 is a perspective view of a light recycling directional controlelement of one embodiment of this invention comprising a lenticular lensarray, light transmitting regions, light absorbing regions and lightreflecting regions comprising asymmetric particles.

FIG. 6 is a perspective view of a light recycling directional controlelement of an embodiment of this invention comprising a lenticular lensarray, light transmitting regions, light absorbing regions, lightreflecting regions and an anisotropic light scattering film adhered tothe lenticular lens array.

FIG. 7 is a perspective view of an edge-lit backlight comprising thelight recycling directional control element of FIG. 3, an LED array, anda waveguide.

FIG. 8 is a perspective view of an edge-lit backlight comprising thelight recycling directional control element of FIG. 3, an anisotropiclight scattering region, a waveguide, and an LED array.

FIG. 9 is a perspective view of a direct-lit backlight comprising thelight recycling directional control element of FIG. 3, an anisotropiclight scattering region, a substrate, and an array of fluorescent bulbs.

FIG. 10 is a cross-sectional side view of an edge-lit light backlightcomprising the light recycling directional control element of FIG. 3, alight collimating element, a diffuser, a waveguide, a white reflectorfilm, and an array of LED's.

FIG. 11 is a cross-sectional side view illustration of a method ofmaking a light recycling directional control element by coating a lightreflecting and light absorbing region and laser ablation.

FIG. 12 is a perspective view of one embodiment of this inventionwherein an edge-lit backlight comprising a light recycling directionalelement has an angular light output profile with two peak luminances atangles away from the normal to the backlight output surface.

FIG. 13 is a cross-sectional side view of a display of one embodiment ofthis invention wherein a display panel is illuminated with thesubstantially collimated backlight of FIG. 10.

FIG. 14 is a perspective view of one embodiment of this inventionwherein a light recycling directional element comprises a lighttransmitting layer with an anisotropic backscattering region.

FIG. 15 is a perspective view of one embodiment of this inventionwherein a light recycling directional element comprises a lighttransmitting layer with an anisotropic backscattering region and a lightblocking region.

FIG. 16 is a perspective view of one embodiment of this inventionwherein the light recycling directional element comprises the lightrecycling directional element of FIG. 14 and a second lenticular lenselement and a second group of lenticular elements.

FIG. 17 is a perspective view of one embodiment of this inventionwherein the light recycling directional element further comprises alight collimating element.

FIG. 18 is a perspective view of one embodiment of this invention of alight emitting device comprising a light recycling directional elementand a light collimating element.

FIG. 19 is a perspective view of one embodiment of this invention of adisplay comprising the light emitting device of FIG. 18 and a liquidcrystal display panel.

DETAILED DESCRIPTION OF THE INVENTION

The features and other details of the invention will now be moreparticularly described. It will be understood that particularembodiments described herein are shown by way of illustration and not aslimitations of the invention. The principal features of this inventioncan be employed in various embodiments without departing from the scopeof the invention. All parts and percentages are by weight unlessotherwise specified.

Definitions

For convenience, certain terms used in the specification and examplesare collected here.

“Speckle”, often referred to also as scintillation, includes the opticalinterference pattern visible on a scattering element or perceived ascoming from or near a scattering element. This can include color orintensity variations within an small area of interest.

“Speckle Contrast” is defined herein to include the ratio of thestandard deviation of the intensity fluctuation to the mean intensityover the area of interest.

“Scatter,” “Scattering,” “Diffuse” and “Diffusing” as defined hereinincludes light scattering by reflection, refraction or diffraction fromparticles, surfaces, or layers.

“Optically coupled” is defined herein as including the coupling,attaching or adhering two or more regions or layers such that theintensity of light passing from one region to the other is notsubstantially reduced due to Fresnel interfacial reflection losses dueto differences in refractive indices between the regions. Opticalcoupling methods include joining two regions having similar refractiveindices, or by using an optical adhesive with a refractive indexsubstantially near or in-between the regions or layers such as OpticallyClear Adhesive 8161 from 3M (with a refractive index at 633 nm of1.474). Examples of optically coupling include lamination using anindex-matched optical adhesive such as a pressure sensitive adhesive;coating a region or layer onto another region or layer; extruding aregion or layer onto another region or layer; or hot lamination usingapplied pressure to join two or more layers or regions that havesubstantially close refractive indices. A “substantially close”refractive index difference is about 0.3 or less, e.g., 0.2 or 0.1.

“Diffusion angle” is a measurement of the angular diffusion profile ofthe intensity of light within a plane of emitted light. Typically thediffusion angle is defined according to an angularFull-Width-at-Half-Maximum (FWHM) intensity defined by the total angularwidth at 50% of the maximum intensity of the angular light outputprofile. For diffusive films and sheets, this is typically measured withcollimated incident light at a specific wavelength or white light.Typically, for anisotropic diffusers, the FWHM values are specified intwo orthogonal planes such as the horizontal and vertical planesorthogonal to the plane of the film. For example, if angles of +35° and−35° were measured to have one-half of the maximum intensity in thehorizontal direction, the FWHM diffusion angle in the horizontaldirection for the diffuser would be 70°. Similarly, the full-width atone-third maximum and full-width at one-tenth maximum can be measuredfrom the angles at which the intensity is one-third and one-tenth of themaximum light intensity respectively.

The “asymmetry ratio” is the FWHM diffusion angle in a first lightexiting plane divided by the FWHM diffusion angle in a second lightexiting plane orthogonal to the first, and thus is a measure of thedegree of asymmetry between the intensity profile in two orthogonalplanes of light exiting the diffuser.

A “spheroidal” or “symmetric” particle includes those substantiallyresembling a sphere. A spheroidal particle may contain surfaceincongruities and irregularities but has a generally circularcross-section in substantially all directions. A spheroid is a type ofellipsoid wherein two of the 3 axes are equal. An “asymmetric” particleis referred to here as an “ellipsoidal” particle wherein each of thethree axis can be a different length. Ellipsoidal particles can range inshapes from squashed or stretched spheres to very long filament likeshapes.

“Planarized,” “Planarization,” and “Planar,” includes creating asubstantially flat surface on an element. A flat surface refers to onethat does not have a substantially varying surface normal angle across asurface of the element. More than one surface may be planarized. Astypically used herein, a material region is combined with a surface ofan element that has a surface structure such that the surface of thematerial opposite the element is substantially planar. Typically,planarized films or components can be easily laminated to anotherelement using pressure sensitive adhesives or hot-lamination withouttrapping air bubbles of sufficient size to affect the opticalperformance of the combined element. Coatings, such as thin coatingsused in some anti-reflection coatings can be applied more uniformly toplanarized elements.

In a first embodiment of this invention, a light recycling directionalcontrol element comprises light absorbing regions, light transmittingapertures disposed on a first side of a substrate and a lenticular lenssurface array disposed on the second side of the substrate. The spacing,width, transmissivity, aperture ratio, substrate thickness, lenticuleprofile (spherical, aspherical, conic, etc), lenticule pitch, refractiveindex, etc. are designed to redirect light transmitted through the lighttransmitting apertures from a first angular range in a first collimatingplane and refract the transmitted light into a second angular range lessthan the first angular range such that the film has a higher degree ofcollimation. Additionally, the aforementioned properties of the lightrecycling directional control element may be chosen to provide spatiallight filtering properties which reduce the appearance of blemishes, orother non-uniformities. In a further embodiment of this invention, thelight transmitting regions are apertures disposed within a lightabsorbing layer off of the axis of the lenses such that the lightreaching the refractive lenticular structures is redirected into asecond angular range such that the peak intensity is off-axis and theangle of peak intensity, theta, is greater than zero degrees to thenormal to the exiting plane of the film or exit surface of a backlightor display. In another embodiment of this invention, the diffusereflectance of the light emitting surface of the light recyclingdirectional control element or backlight comprising the same, whichcomprises the refractive surface of the lenticular lens array is lessthan 50% such that the light emitting device maintains a gray, darksilver, or black appearance when illuminated from the light exitingside. In a further embodiment, the diffuse reflectance (d/8) of thelight emitting region of the light emitting device is less than 20% suchthat the visibility or contrast of blemishes, yellowing, dirt, etc areminimized when the light emitting device is not emitting light in a offstate. In a further embodiment, the light emitting device is lessconspicuous and provides less reflectance of ambient light. In a furtherembodiment of this invention, the reflectance of the element, orbacklight or display using the same is less than 20% such that thedisplay contrast is improved. By increasing the absorption of ambientlight in regions corresponding to black or dark pixels, the contrastratio of the display is improved. In a further embodiment of thisinvention, the ambient light reflectance (d/8) of a backlight comprisinga light recycling directional control element is at least one of 10%,20%, 30%, 50% or 60% less than that of the same backlight without thelight recycling directional control element. This is especially usefulfor displays used in environments where the flux of ambient lightincident on the display is very high or in displays where improvedcontrast is desired.

In one embodiment of this invention a method for producing a lightabsorbing layer on a light recycling directional control elementcomprises the steps of depositing a light absorbing material on alenticular lens array film and further depositing a light reflectingmaterial on the light absorbing material. Light transmitting aperturesare formed within the light absorbing layer and the light reflectinglayer through laser ablation. The width, location, thickness, andtransmissivity of the apertures are designed to provide a predeterminedangular light output profile, uniformity and appearance when viewed froma direction opposite that of the input light.

In one embodiment of this invention, a light recycling directionalcontrol element comprises a lenticular lens surface profile, lightreflecting regions disposed to receive light and reflect a portion ofthe incident light and light transmitting regions disposed in-between orwithin the light reflecting regions disposed to transmit a portion ofthe incident light. A portion of the light incident on the lightreflecting layer is transmitted through the light reflecting layer andreaches the light absorbing layer and is substantially absorbed. Theportion of the incident light which is transmitted through the lighttransmitting regions reaches the lenticules wherein the first angularbundle of rays of a second predetermined angular width is refracted intoa second angular bundle of rays of a second predetermined angular widthwherein the second angular width is less than the first in a planeperpendicular to the lenticules.

In one embodiment of this invention a light recycling directionalcontrol element comprises a surface relief lenticular lens array, lighttransmitting regions disposed to transmit light from a predeterminedangular range and at least one of a light absorbing or light reflectingregion.

Lenticular Structure

In one embodiment of this invention, the lenticular lens array surfacerelief structure on a light recycling directional control elementcomprises a substantially linear array of convex refractive elementswhich redirect light from a first angular range into a second angularrange. As used herein, lenticular elements or structures include, butare not limited to elements with cross-sectional surface relief profileswhere the cross-section structure is hemispherical, aspherical, conical,triangular, rectangular, polygonal, or combination thereof. Lenticularstructures may be linear arrays, two-dimension arrays such as amicrolens array, close-packed hexagonal or other two-dimensional array.The features may employ refraction along with total internal reflectionsuch that the output angular range is less than the input angular rangewithin one or more exiting light planes. Lenticular structures may alsobe used to redirect light to an angle substantially off-axis from theoptical axis of the element. As used herein, lenticular may refer to anyshape of element which refracts or reflects light through total internalreflection and includes elements referred to as “non-lenticular” in U.S.Pat. No. 6,317,263, the contents of which are incorporated by referenceherein. The lenticular structure may be disposed on a supportingsubstrate. The lenticular element may have a first focal point in thenear field and a group of lenticular elements may collectively have afar-field focal point defined as a region where the spatialcross-sectional area of the light flux is at a minimum. In oneembodiment, the focal point of the structures is substantially near theopposite surface of the supporting substrate. The material, methods ofmaking and structures of lenticular lens arrays, microlens arrays,prismatic films, etc. are known in the art of backlights, projectionscreens and lenticular and 3D imaging.

In one embodiment of this invention, the light recycling directionalcontrol element comprises more than one lenticular structure disposed onthe same or opposite side of a substrate. A light recycling directionalcontrol element with a lenticular element disposed on the input surfacecan focus more light through the light transmitting regions and changethe direction or FWHM angular width of the light output profile from thelight recycling directional control element. The structures can beconvex or concave and similar to those used in double-lenticular rearprojections screens such as those described in U.S. Pat. Nos. 5,611,611,5,675,434, 5,687,024, 6,034,817, 6,940,644, and 5,196,960, the contentsof which are incorporated herein by reference. The design of thelenticular shape on one or more surfaces is not limited to thesefeatures and includes other designs known in the rear-projection screenand lenticular imaging industry and the design may include thosereferenced in other patents referred to in other sections of thisapplication and incorporated by reference herein.

Substantially clear lens substrates are known in the art and are used inthe production of lenticular screens for rear-projection screens. In oneembodiment of this invention, a volumetric diffuser is used as thesupporting substrate. In this embodiment, the number of films may bereduced or the thickness reduces by alleviating or reducing the need fora substrate which is not optically active and replacing it with adiffuser which improves the uniformity. By using an anisotropicvolumetric diffuser (which scatters light into higher angles in a firstoutput plane parallel to the lenticules, and has very little or oneffect on the scattering of light along the plane perpendicular to thelenticules), the focusing or collimating power of the lenticular lensarray in the second light output plane perpendicular to the lenticulescan be maintained while the spatial luminance uniformity of thebacklight is improved. In one embodiment of this invention, the angularFWHM of the diffusion profile of the anisotropic diffuser used as thelenticular lens array substrate in the plane parallel to the lenticulesis greater than one selected from the group of 5, 10, 20, 30 and 50 andthe angular FWHM of the diffusion profile of the anisotropic diffuserused as the lenticular lens array substrate in the plane perpendicularto the lenticules is less than one selected from the group of 10, 5, 4,2, and 1. In a further embodiment, the asymmetry ratio of theanisotropic light scattering diffuser disposed as a substrate to thelenticular lens array in a light recycling directional control elementis greater than one selected from the group 5, 10, 20, 40, 50, and 60.Additionally, the FWHM of the total scattering angles in the first andsecond output planes of a backlight comprising the light recyclingdirectional control element of one embodiment of this invention can beindependently controlled by use of an anisotropic diffuser. In a furtherembodiment of this invention, a light recycling directional controlelement comprises a lenticular lens array wherein the lenticular lenseshave a conformal low refractive index region disposed on the curvedsurface of the lenticule such that the output surface is substantiallyplanarized. In a further embodiment of this invention, the outputsurface of a planarized light recycling directional control element isthe output surface, or a substantially co-planar surface coupled to apolarizer, display or other optical component in a backlight or displaycomprising the element.

In another embodiment of this invention, a light recycling directionalcontrol element comprises a layer of beads, a light transmitting region,and a light reflecting region wherein the beads are disposed to refractincident light from a light transmitting region. Analogous to thelenticular lens array, an array comprising a randomized assortment ofbeads may be used to collimate or substantially reduce the angularextent of light exiting from a light transmitting region and filter thelight. The primary differences include the fact that the bead type lightrecycling directional control element will reduce the angular extent ofthe output light in all planes of the output light normal to the exitingsurface. However, the ability to achieve very high levels of collimationis limited and the fill-factor, and ultimate transmission is limited dueto the cross-sectional area limitations of close-packing an array ofspheres (or hemispheres or spheroidal lens-like structures). In anotherembodiment of this invention, a light recycling directional controlelement comprises lenticular or bead based elements and lighttransmitting regions and light absorbing regions in common with rearprojection screens such as those described elsewhere herein and thosedescribed in U.S. Pat. No. 6,466,368. In some embodiments of thisinvention, unlike in the case of the optical element used withprojection screens where the input light is typically collimated or of areduced angular extent, non-collimated light is incident first upon thelight transmitting apertures and subsequently is transmitted through thelenticular or bead elements. In the comparison with the rear projectionscreen, the optical element of one embodiment of this invention is usedin a reverse illumination format to that of a rear projection screenelement. In on embodiment of the present invention, the incident lighthas an angular FWHM greater than 30 degrees and is incident first on thelight transmitting regions and the output light has a reduced angularextent and exits through the lenticular or bead based refractiveelements.

Common materials such as those used to manufacture lenticular screenssuch as vinyl, APET, PETG, or other materials described in patentsreferenced elsewhere herein may be used in the present invention for alight recycling directional control element In a further embodiment, amaterial capable of surviving temperature exposures higher than 85degrees Celsius may used as the lenticular lens or substrate to thelenticular lens or bead based element such as biaxially oriented PET orpolycarbonate. By using a material capable of withstanding hightemperature exposure, manufacturing processes such has heating during apressure application stage or heating during an exposure stage may beused to decrease the production time.

Pitch of the Lenticular Structure

The pitch of the lenticular lens structure will have an effect on thefocusing power, the thickness of the lenticular lens array and substrateand other optical properties such as moiré. In one embodiment of thisinvention, the lenticular lens array structure is in the form ofconcentric lenticular lenses. In this embodiment, the lenses areparallel, but are arranged in an arc or circle. The pitch of the lensesand other properties may vary similarly to linear lenticular lenses. Abacklight comprising a light recycling directional control elementcomprising concentric lenticular lenses can provide a spatial filteringalong radial directions as opposed to linear directions. In oneembodiment of this invention, a backlight comprising a substantiallycentrally located light source and a light recycling directional controlelement comprising a concentric lenticular lens has a spatial luminanceuniformity greater than one selected from 60%, 70%, 80% and 90%. Theconcentric lenticular lens may be manufactured using injection molding,stamping, embossing or other similar techniques known in the opticalindustry suitable for making Fresnel lenses. In one embodiment of thisinvention, a light recycling directional control element or backlightcomprising the same, comprises a concentric lenticular lens array and atleast one of a light reflecting, light absorbing, or light transmittingregion wherein the regions are substantially ring or arc-shapedcorresponding to the concentric lenticular lens.

In one embodiment of this invention, a light recycling directionalcontrol element comprises a linear lenticular lens, light transmittingregions, and a light collimating element wherein the spacing between thecenters of the light transmitting regions is substantially equal to thepitch of the lenticular lenses in the light recycling directionalcontrol element and this pitch is predetermined such that the pitch ofthe optical interference moiré pattern is less than 100 μm and is verydifficult or imperceptible to the naked eye from a reasonable viewingdistance to a person viewing a backlight incorporating the element. Inone embodiment of this invention, the light recycling directionalcontrol element comprises a lenticular array and collimating elementsuch as a 90 degree apex angle prismatic collimation film. In anotherembodiment of this invention, a backlight comprises a light recyclingdirectional control element and a light collimating element. Thecollimating element may be disposed above or below the lenticular lensarray. The visibility of the moiré interference pattern can be visuallydistracting in a backlight and reduces the luminance uniformity. Thevisibility, or luminance contrast of the moiré patterns is defined asLMmax−LMmin/(LMmax+LMmin) where LMmax and LMmin are the maximum andminimum luminance, respectively, along a cross section substantiallyperpendicular to the repeating moiré pattern when illuminated withdiffuse incident light. In one embodiment of this invention, the moirécontrast of the light recycling directional control element, or a lightemitting device comprising the element thereof, is low such that themoirécontrast is less than one selected from the group of 50%, 40%, 30%,20% and 10%. The moirécontrast may be reduced by shifting the pitch ofthe moiré pattern such that it is sufficiently small enough not to bevisible to the naked eye or be seen without close inspection. This canbe accomplished one or more of the following methods: adjusting thepitch of one or more elements, rotating one of the elements relative tothe other, randomizing the pitch, or increasing the spacing between thetwo elements.

Adjusting the Pitch of Lenticular Lens Array to Reduce MoiréContrast

By adjusting the pitch of one or both the lenticular lens array and thelight collimating element, the moiré contrast can be reduced. In orderto avoid the moiré, the ratio of the pitches between the two arrays ofthe elements should be equal to 1/(N+0.5) where N is an integer. A pitchratio from 0.9/(N+0.5) to 1.1/(N+0.5) will have a relatively lowvisibility of moiré. The regular array pitch of either element may be P1or P2 in accordance with the above equation to achieve a minimum levelof moiré visibility. In one embodiment of this invention, a lightrecycling directional control element comprises a lenticular lens arraysurface of a first pitch P1 and a light collimating element of a secondpitch P2 wherein 0.9/(N+0.5)<P2/P1<1.1/(N+0.5) where N is an integer. Inanother embodiment of this invention, a light recycling directionalcontrol element comprises a lenticular lens array surface of a firstpitch P1 and a light collimating element of a second pitch P2 wherein0.95/(N+0.5)<P2/P1<1.05/(N+0.5) where N is an integer.

In another embodiment of this invention, a light recycling directionalcontrol element comprises a lenticular lens array surface of a firstpitch P1 and a light collimating element of a second pitch P2 whereinP2/P1=1/(N+0.5) where N is an integer. In one embodiment of thisinvention, a light recycling directional control element comprises alenticular lens array surface with a 187 micron pitch (P1) and a lightcollimating element with an approximately 25 micron pitch (P2) whereinP2/P1=0.133=1/(N+0.5)=where N is 7. In one embodiment of this invention,a light recycling directional control element comprises a lenticularlens array surface with a 425 micron pitch (P1) and a light collimatingelement with a 50 micron pitch (P2) wherein P2/P1=0.1176=1/(N+0.5)=whereN is 8. In one embodiment of this invention, a light recyclingdirectional control element comprises a 60 lpi (lines per inch)lenticular lens array film with a 90 degree prism light collimatingelement with a 50 micron pitch. In a further embodiment of thisinvention, a backlight comprises a light recycling directional controlelement with a 60 lpi (lines per inch) lenticular lens array film andfurther comprises a 90 degree prism light collimating element with a 50micron pitch.

In one embodiment of this invention, a light recycling directionalcontrol element (or backlight comprising the same) comprises alenticular lens array surface with a 237 micron pitch (P1) and a lightcollimating element with a 356 micron pitch (P2) whereinP2/P1=1.5=(N+0.5)=where N is 1. Various combinations of pitches oflenticular lens arrays and light collimating elements can result in areduced moiré contrast and are within the scope of this invention.Several examples are disclosed in Table 1.

TABLE 1 P1 P2 = 25 P2 = 50 P2 = 356 P2 = 356 N 1/(N + 0.5) N + 0.5 μm μmμm μm* 1 0.6667 1.5 38 75 534 237 2 0.4000 2.5 63 125 890 142 3 0.28573.5 88 175 1246 102 4 0.2222 4.5 113 225 1602 79 5 0.1818 5.5 138 2751958 65 6 0.1538 6.5 163 325 2314 55 7 0.1333 7.5 188 375 2670 47 80.1176 8.5 213 425 3026 42 9 0.1053 9.5 238 475 3382 37 10 0.0952 10.5263 525 3738 34 As described in Table 1, several different lightcollimating element pitches (P2) can be used with a range of lenticularlens array pitches (P1) to produce a light recycling lens array pitches(P1) to produce a light recycling directional control element orbacklight with reduced moiré contrast. In reference to the far rightcolumn, P2 = 356 μm*, the pitches displayed are determined by P1 =P2/(N + 0.5) while in the other columns, P1 is determined by therelationship P1 = P2*(N + 0.5).Adjusting the Angle Between the Orientation of the Arrays within TheElements to Reduce Moiré Contrast

By rotating one of the lenticular lens element or light collimatingelement relative to the other such that the angle between the arrays isgreater than 0 degrees, the moiré contrast can be reduced. In oneembodiment of this invention, a light recycling directional controlelement (or backlight comprising the same) comprises a lenticular lensarray and a light collimating element disposed in two planessubstantially parallel to each other such that the angles between thetwo arrays, φ1 is greater than one selected from group of 0 degrees, 5degrees, 10 degrees, 20 degrees, 45 degrees and 60 degrees and 80degrees.

Using a Random or Semi-Random Pitch of the Lenticular Lens Array ToReduce Moiré Contrast

A lenticular lens array with a constant pitch can interfere with aconstant pitch array of another refractive or TIR based element such asa 90 degree prismatic collimation film. In one embodiment of thisinvention, the moiré pattern viewable on a light recycling directionalcontrol element between a the lenticular lens array and a collimatingelement or similar array of light refracting elements is alleviated byeffectively randomizing the pitch, height, or spacing between the apexor valleys of at least one of the elements. Similarly, the moirécontrast can be reduced producing a random or predetermined variation onthe pitch or slop angle of a refracting or TIR element as described inreference to brightness enhancing films in U.S. Pat. Nos. 5,919,551,6,354,709, 5,771,328, 7,092,163, and 6,862,141.

Increasing the Separation Between the Lenticular Lens Array and AnotherOptical Lens Array to Reduce Moiré Contrast

By increasing the distance between the lenticular lens array and therefractive or TIR based element, the contrast of the moiré pattern isreduced. In one embodiment of this invention, the moiré contrast of thelight recycling directional control element or the moiré contrastbetween a separate optical component and the light recycling directionalcontrol element is reduced to less than 50% by separating theinterfering elements by at least the lower of the two interferingpitches. In another embodiment of this invention, the moiré contrast ofthe light recycling directional control element (or backlight using thesame) or the moiré contrast between a separate optical component and thelight recycling directional control element is reduced to less than 50%by separating the interfering elements by at least twice the lower ofthe two interfering pitches. The optical elements may be separated by anair gap or by a substantially transparent, clear material, or they maybe separated by a diffusing material such as a volumetric anisotropiclight scattering element either within the light recycling directionalcontrol element or in-between the light recycling directional controlelement and a separate optical component with a regular array of surfacerelief structures. The spacing element may also provide an additionalfunction such as a carrier layer, substrate, protective layer, orproviding additional diffusion or refractive or TIR based lightre-direction.

In one embodiment of this invention, in a light recycling directionalcontrol element (or backlight incorporating the element), the pitch ofthe lenticular lens array in combination with the transmissive regionsspatially filters the intensity of the incident light and removes theappearance of non-uniformities due to other optical films or the spatialseparation of extraction features on a waveguide. In one embodiment ofthis invention (or backlight incorporating the element), a lightrecycling directional control element comprises a lenticular array ofpitch P1, at least one of a light reflecting and light absorbing regionand a light transmitting region of width A1 measured along an axisperpendicular to the lenticules, optically coupled to a waveguide withlight extraction features with a maximum linear dimension D_(max)measured in the plane of the waveguide with a maximum separationdistance of S_(d) such that at least one of P1<S_(d), P1<D_(max),A1<D_(max) and A1<S_(d). In a further embodiment of this invention, abacklight comprising the light recycling directional control element inthe previous embodiment has at least one of a spatial luminanceuniformity=100%×[1−(Lmax−Lmin)/Lmax+Lmin)] of greater than 70% and acolor uniformity of Δu′v′<0.1 between any two points as measured by ahorizontal and vertical cross sectional color and luminance measurementpassing through the center of the light emitting surface of thebacklight using an imaging photometer wherein the measurement pixelsize, PS, in the smaller dimension, is less than 0.1 mm. A photometricimaging pixel size of less than 0.1 mm will resolve the smallest blemishor non-uniformity that is likely to be visible in most backlight ordisplay applications.

In one embodiment of this invention, a backlight comprises a lightrecycling directional control element of pitch P1 and a prismatic lightcollimating film of pitch P2 wherein P1 is not equal to P2. In anotherembodiment of this invention, P1>P2 such that the luminance contrast(CL) of the moiré pattern is less than one selected from the groupconsisting of 0.8, 0.5, 0.2, 0.1 and 0.05 where the luminance contrastof the moiré pattern is defined as CL=(Lmax−Lmin)/(Lmax+Lmin) and Lmaxis the maximum luminance between two successive dark moirépatterns andLmin is the minimum luminance of the dark pattern measured along a lineperpendicular to the pattern.

In one embodiment of this invention, a backlight comprises a lightfiltering collimating lens with a pitch of P1 and a light guide withlight extraction features with a pitch ranging from Pmin to Pmax wherePmin is the minimum spacing between two light extraction features andPmax is the maximum spacing between two adjacent light extractionfeatures. When the pitch of the light filtering collimating lens is veryclose to the pitch between two light extraction features, a moirépattern can be visible. In one embodiment of this invention, a backlightcomprises a light filtering collimating lens with a pitch P1 and a lightguide with light extraction features with a maximum spacing of Pmax andP1>Pmax. In another embodiment of this invention, a backlight comprisesa light filtering collimating lens with a pitch P1 and a light guidewith light extraction features with a minimum spacing of Pmin andP1<Pmin.

Lenticular Lens Alignment

In an additional embodiment of this invention, the alignment of thelenticular lens array is rotated with respect to an exit aperture of thelight emitting device. In one embodiment, the lenticular lens is alignedat an angle φ1 to the longer dimension of the light exiting aperture ofthe light emitting device. In an additional embodiment, φ1 is oneselected from the group consisting of 0 degrees, 45 degrees, and 90degrees. In another embodiment of this invention, a backlight comprisesa light recycling directional control element wherein the lenticularlens array is aligned at an angle φ2 relative to a 90 degree apex angleprismatic collimating film wherein 90 degrees>φ2>0 degrees and thecontrast of the spatial luminance moiré pattern of the backlight is lessthan one selected from the group consisting of 0.8, 0.5, 0.2, 0.1 and0.05.

Light Blocking Region

The light blocking region may be a light transmitting region or a lightreflecting region, or a combination of both. In one embodiment of thisinvention, the light blocking region transmits less than one selectedfrom the group of 40%, 30%, 20% and 10% of the incident specular ordiffuse light.

Light Transmitting Layer

In one embodiment of this invention, an optical element comprises alight transmitting layer disposed between lenticular elements and afirst input surface. The light transmitting layer may comprise lightblocking regions or light transmitting regions. The light blockingregions may be light absorbing regions, light reflecting regions,partially light absorbing regions, partially light reflecting regions ora combination thereof. The light transmitting layer may comprise a lightblocking region comprising a light absorbing region disposed between alight reflecting region and the lenticular elements. The lightreflecting regions may be diffusely reflective or specularly reflectiveand the light transmitting regions may be specularly transmitting ordiffusely transmitting. A light absorbing region or light blockingregion, as used herein, may include a region that absorbs a firstportion of light and transmits or reflects a second portion of light. Alight reflecting or light blocking region, as used herein, may include aregion that reflects a first portion of light and transmits or absorbs asecond portion of light.

Light Transmitting Regions

The light transmitting regions permit light from a specific spatialregion to be transmitted through to the lenticular lens array. In orderto provide a light recycling directional control element with high lightthroughput efficiency, a sufficient amount of light must be able to betransmitted through the light transmissive regions. In one embodiment ofthis invention, the total luminous transmittance of the clear lighttransmitting regions measured according to ASTM D1003 before theapplication of the light blocking regions is at least one of 50%, 70%,80%, 85%, 90%, 95% when measured with the incident light passing throughthe lenticular lens before the transmissive aperture region. In oneembodiment of this invention, the aperture region is diffuselytransmissive such that the light is diffused as it passes through theaperture region. Haze is one method for measuring the amount ofdiffusion in a sample. In one embodiment of this invention, the haze ofthe of the clear aperture regions measured according to ASTM D1003 witha BYK Gardner Hazemeter before the application of the light blockingregions is at least one of 5%, 10%, 20%, 50%, 80%, 90%, or 99% whenmeasured with the incident light passing through the lenticular lensbefore the transmissive aperture region. In another embodiment of thisinvention, the aperture region comprises an anisotropic light scatteringregion. The anisotropic light scattering region transmits and scatterslight anisotropically to provide improved uniformity and a predeterminedangular light distribution performance. In a further embodiment of thisinvention, the asymmetry ratio of the FWHM diffusion profiles of theanisotropic light scattering region is greater than one selected fromthe group consisting of 2, 5, 10, 30, 50, and 60.

The width of the light transmitting region is selected to provide apredetermined light output angular profile while maintaining asufficient level light filtering and light transmission through thelight filtering collimating lens. The fill factor is defined as theratio of the light transmitting region width to the width of the lightabsorbing or reflecting region between the apertures along a first axisparallel to the array of lenticules. In order for the light filteringcollimating lens to provide a high degree of collimation, theCollimation Factor, CF, should be sufficiently high assuming a constantfocal point, lens shape and refractive index. The Collimation Factor isa relational metric used to compare the ability of a lenticular lensarray to collimate light from a specific light transmitting regionassuming a constant lenticule curvature and focal distance. TheCollimation Factor is defined as the ratio of the pitch of thelenticular lens P1, to the aperture width, A1, or P1/A1. In oneembodiment of this invention, the pitch of the lenticular lens isapproximately 187 μm, the aperture width of the light transmittingregion is 25 μm and the linewidth of the light absorbing (or reflecting)region is 162 μm and the CF is 7.5. In one embodiment of this invention,the CF is greater than one element selected from the group consisting of1.5, 3, 5, 6, 8 and 10.

The location of the aperture in relation to the lenticular lens elementsor arrays contributes to the directionality of the output light. In oneembodiment of this invention, the aperture is centered along the opticalaxis of the lenticules in an optical element. In another embodiment ofthis invention, the light output distribution is off-axis and is definedby an angle, γ1, defined from the apex of the lenticule to the center ofthe apertures and measured from the normal of the substantially planaroptical element. In one embodiment of this invention, the angle γ1 isgreater than one angle selected from the group comprising 5°, 10°, 15°,20°, 30°, and 40°. In one embodiment of this invention, a backlightcomprises a light recycling directional control element wherein γ1 isgreater than 5 degrees and the angle of peak intensity of light outputfrom the backlight is at an angle θ measured from a normal to theexiting surface of the backlight where θ is greater than 0 degrees. Inanother embodiment of this invention, θ is greater than 5 degrees and abacklight and display incorporating the light recycling directionalcontrol element is design to provide a peak luminance off-axis. Fordisplays used in applications such as vehicles, fixed instrument panels,etc, it is often desirable to have the peak intensity at an angle fromthe normal to the substantially planar display surface. In a furtherembodiment of this invention, the aperture is located substantially nearthe midpoint between the lenticules. In this embodiment, upon wide angleinput illumination, the light recycling directional control elementproduces a twin-lobe output with two maximums intensities. A backlightincorporating this element can be used to produce a display wherein thelight output produces two lobes for viewing at two different angles. Inapplications such as a display mounted between the driver and passengerseats of a car, by directing light into the two lobes directedsubstantially toward the driver and passenger, the optical efficiency ofthe system is improved, thus allowing for lower power used or a reducednumber of light sources. In a further embodiment of this invention, onemore light recycling directional control elements are used to provideoff-axis directionality in a first plane and at least two peak viewinglobes in a second plane orthogonal to the first.

In one embodiment of this invention, the angular light output profile ofthe light recycling directional control element is controlled byspatially varying at least one of the size, shape, pitch, andtransmittance of the light transmitting apertures. By having regions,with wider apertures, for example, the light output from that regionwill have a lower degree of collimation (smaller collimation factor) andhigher flux output through less recycling. This technique may be used tospatially adjust the uniformity of backlight. In one embodiment, anedge-illuminated backlight comprises a light recycling directionalcontrol element wherein the aperture width increases in edge. In thisembodiment, the method used to create the linewidths of at least one ofthe light blocking, light reflecting, light absorbing, or lighttransmitting regions can be used to improve the spatial luminanceuniformity of the backlight. Additionally, the angular output indifferent regions may be controlled more easily by increasing theaperture width in some regions and reducing the aperture width along atleast one axis in order to provide a backlight with a precisely tailoredoutput profile. This can simplify the angular adjustment of the outputfrom a backlight in one or more regions by converting it to a spatialadjustment in the printing, transfer, exposure, etc. method used tocreate the lines and thus apertures. In another embodiment of thisinvention, at least one of the linewidth and location relative to theoptical axis of its respective lenticule of the light transmittingregion varies along a direction parallel to the lenticular array toprovide a focusing or concentrating affect to the light output profile.As discussed herein, by shifting the light transmitting region to oneside of the axis of a lenticule, light can be directed off-axis. Byshifting the light transmitting regions spatially in two regions awayfrom each other in different areas of a backlight, the light exiting thelenticules from those corresponding regions can be directed toward aspecific location, thus essentially creating a positive focal point forthe light output within at least one plane. In the case where the lighttransmitting regions move closer towards each other, the light outputfrom the corresponding lenticular lens array regions diverges relativeto each other, thus creating a type of negative (or virtual focus). Inone embodiment of this invention, a substantially planar backlightcomprises a light filtering collimating region with a positive focaldistance within at least one plane. In one embodiment of this invention,a substantially planar backlight comprises a light filtering collimatingregion with a negative focal distance along at least one plane. Apositive or negative focal distance can be used in a backlight toprovide increased control over the light output and can be used toconcentrate or further spread out light within one or more outputplanes.

In a further embodiment of this invention, a light recycling directionalcontrol element comprises light reflecting regions substantially alignedbeneath the apex of the lenticules (or beads) with light transmittingapertures on either side such that light arriving from opposite sides ofa lightguide which exits the lightguide with a peak luminance outputangle between an 20 and 80 degrees is substantially collimated. Bydesigning the width and location of the light reflecting regions and thecurvature (or slope in the case of prismatic elements) the light fromthe waveguide can be designed to be re-directed substantially normal tothe backlight.

Light Reflective Region

The light reflecting region of one embodiment of this invention mayspecularly reflect, isotropically scatter back or anisotropicallyscatter back, or some combination thereof, direct light backwards. Inone embodiment of this invention, light reflecting regions are disposedsubstantially in-between the light transmitting aperture regions in alight recycling directional control element. The reflective regions maybe diffusely reflective or specularly reflective and the diffuselyreflective profile may be symmetric or anisotropic. Typically inbacklights, the light reaching the optical elements arrives from a widerange of angles and therefore, the diffuse luminance reflectancemeasured in a d/8 geometry (shortened here to diffuse reflectance) is amore representative measurement of the reflectance from the component ina backlight application than 1 minus the specular transmittance such asdefined and sometimes measured according to the ASTM D1003 standard. Thediffuse reflectance of an element, region, or combination of regions canbe measured placing the element or region(s) over an aperture of a “darkbox” wherein the interior is filled with light absorbing material suchas a black felt and measuring the diffuse reflectance (specularcomponent included) of the element using a Minolta CM-508d diffusereflectance spectrophotometer.

A diffusely reflecting region as defined herein is one wherein laserlight with a divergence less than 10 milliradians incident upon theregion reflects with a larger angular diffusion profile such that theFWHM of the diffuse reflecting profile is greater than 2 degrees withinat least one plane of reflection. In one embodiment of this invention,the diffusely reflecting region anisotropically reflects light such thatthe angular FWHM of the diffuse reflectance is higher in a firstreflectance plane than a second reflectance plane orthogonal to thefirst. In one embodiment of this invention, a light recyclingdirectional control element comprises light reflecting regions of ananisotropically reflecting diffuser with a FWHM diffusion profile of atleast 5 degrees within a first reflecting plane and an asymmetry ratioof greater than 1. In this embodiment, the light transmitting aperturesare disposed between the anisotropic light scattering regions. Inanother embodiment of this invention, a light filtering collimating lenscomprises light reflecting regions of an anisotropically reflectingdiffuser with a FWHM diffusion profile of at least 5 degrees within afirst reflecting plane and an asymmetry ratio of greater than 1 whereinthe reflecting diffusion plane with the larger FWHM angular diffusionprofile is oriented perpendicular to the lenticules in the lenticularlens array. In this embodiment, the light reflected from theanisotropically reflecting regions is more efficiently directedangularly toward the clear apertures wherein more light may pass throughthe light transmitting apertures than in the case of a symmetricallydiffusing light reflecting region wherein light is additionally diffusedin a direction parallel to the lenticules and parallel to the diffuselyreflecting region. The light scattering parallel to the reflectingregions will require significantly more reflections in order to exitthrough the light transmitting apertures. These multiple reflectionscause more of the light to be absorbed within the materials.

In one embodiment of this invention, a light recycling directionalcontrol element comprises a substantially diffusely reflecting region.In a further embodiment of this invention, a backlight comprises a lightrecycling directional control element with substantially transparentregions disposed between light reflecting regions wherein the diffusereflectance of the light recycling directional control element isgreater than one selected from the group consisting of 40%, 50%, 60%,70%, 80%, 90%, and 95% when measured with diffusely incident light onthe side of the lenticular lens array comprising the light reflectingregion.

The light transmitting regions can reflect a portion of the incidentlight in a specular, symmetrically diffuse, or anisotropic scatteringreflecting profile. In light recycling directional control elementscomprising light reflecting regions and light transmitting regions whichare partially transmitting and partially reflecting, the reflectancefrom the combination will increase the luminance and color uniformitywhen used in a backlight. In one embodiment of this invention, abacklight comprises a light recycling directional control element withpartially transparent regions disposed between diffusely reflectingregions wherein the diffuse reflectance of the combination of the lightreflecting region and the light transmitting region is greater than oneselected from the group consisting of 40%, 50%, 60%, 70%, 80%, 90%, and95%. In one embodiment of this invention, a backlight comprises a lightrecycling directional control element with light transmitting regionsdisposed between light reflecting regions wherein the light transmittingregions have a diffuse reflectance greater than 10% and the diffusereflectance of the combination of the light reflecting region and thelight transmitting apertures is greater than 80%. In this embodiment,more light is recycled than in the case of substantially transparent orlow reflectance light transmitting regions and therefore the luminanceand color uniformity of a backlight incorporating the element isimproved while still providing a sufficient amount of light to passthrough the apertures and exit the backlight. In a further embodiment ofthis invention, a backlight comprises a light recycling directionalcontrol element with a lenticular lens array and light reflectingregions disposed in-between light transmitting regions wherein the lighttransmitting regions contain asymmetric particles and the reflectedlight from the light transmitting region is reflected anisotropicallyand the diffuse reflectance of the light transmitting region is greaterthan 10% and less than 80%.

In another embodiment of this invention, a backlight comprises a lightrecycling directional control element comprising a lenticular lens arrayand light transmitting regions disposed between light reflecting regionswherein the diffuse reflectance of the light reflecting region and thelight transmitting region is greater than one selected from the groupconsisting of 40%, 50%, 60%, 70%, 80%, 90%, and 95%.

In light recycling directional control elements which have lighttransmitting regions made of substantially transparent material wherethe light transmittance is greater than approximately 92% (includingFresnel reflections), the diffuse reflectance of the light reflectingregions disposed between the light transmitting regions can becalculated. The diffuse reflectance of the light reflecting regionDR_(LR) can be calculated by dividing the diffuse reflectance of thetotal of both regions (DR_(T)) by the area ratio of the light reflectingregion, 1−AR_(T) where AR_(T) is the percentage of area of the totalregion occupied by the light transmitting region and thus the diffusereflectance of the light reflecting region, DR_(LR)=DR_(T)/(1−AR_(T)).In another embodiment of this invention, a backlight comprises a lightrecycling directional control element which comprises a lenticular lensarray and light transmitting regions disposed between light reflectingregions wherein the diffuse reflectance of the light reflecting regionsis greater than one selected from the group consisting of 80%, 90%, and95% as measured by the aforementioned method.

In one embodiment of this invention, the diffuse reflectance(calculated) is less than 80% based on a measurement of the reflectedlight from light incident on the light transmitting layer comprisinglight reflecting regions without directly passing through thelenticules. In a further embodiment of this invention, the diffusereflectance (calculated) of the light transmitting region comprisinglight absorbing regions is greater than 20% based on a measurement ofthe reflected light from light incident on the light transmitting layerwithout directly passing through the lenticules.

In one embodiment of this invention, the diffuse reflectance of thediffusely reflecting regions is less than 95% such that more than 5% ofthe light is transmitted through the diffusely reflecting regions. Byincreasing the light transmittance (lowering the diffuse reflectance),light is transmitted at the higher angles from the normal in addition tothe light passing through the clear apertures which is more collimated.The light transmitting through the diffuse regions will lower the moirécontrast between the light recycling directional control element andanother optical element in the system. In one embodiment of thisinvention, the light output profile of a backlight comprising a lightrecycling directional control element has a softer angular cut-off dueto the diffusely reflecting regions having a light transmittance greaterthan 5%. In a further embodiment of this invention, the light outputprofile of a backlight comprising a light recycling directional controlelement comprising reflecting regions having a light transmittancegreater than 5% has an angular output region with a slope of less thanone selected from the group of 10% per degree, 5% per degree, 2% perdegree, and 1% per degree where the % drop refers to the percentage ofthe intensity relative to the peak intensity in the angular regionbetween the peak intensity and the angular points at 10% intensitywithin at least one output plane.

The light reflective region may comprise a reflective ink, beads orother additives that substantially reflect light of one or morewavelength ranges. The reflective additive used in an ink or polymersystem may include BaSO₄, TiO₂, organic clays, fluoropolymers, glassbeads, silicone beads, cross-linked acrylic or polystyrene beads,alumina, or other materials known in the diffusion screen or filmindustry for backlights or projection screens such that the refractiveindex difference between them and a supporting polymer matrix or binderis sufficiently high to reflect light. The light reflecting region mayalso be a light reflecting material such as PTFE, or it may comprise ablend of thermoplastic polymers such as described in U.S. patentapplication Ser. No. 11/426,198, or U.S. Pat. Nos. 5,932,342, 5,825,543,and 5,268,225, the text of each is incorporated by reference hereinwhere the refractive index between the two polymers is chosen to be veryhigh such that the light reflects from the film. In another embodimentof this invention, the light reflecting region is a voided film suchthose described in U.S. Pat. Nos. 7,273,640, 5,843,578, 5,275,854,5,672,409, 6,228,313, 6,004,664, 5,141,685, and 6,130,278, and U.S.patent application Ser. No. 10/020,404, the contents of each areincorporated by reference herein.

The light reflecting region may comprise nanoparticle dispersions suchas nanodispersions of aluminum or silver or other metals that can createa specularly reflecting ink. In one embodiment of this invention, abacklight comprises a specular light reflecting region which recyclesthe incident light from within the backlight to provide uniformity andthe light output from the backlight is substantially collimated from thelight filtering collimating film. In a further embodiment, lightrecycling directional control element serves to recycle and providedincreased uniformity in a small form factor (reduced total thickness ofthe backlight) as well as reducing the angular output of light such thatthe output light is more collimated. In a further embodiment of thisinvention, a backlight comprises a light recycling directional controlelement with a specularly reflective region wherein the fill factor ofthe specularly reflective region is greater than 50%.

In one embodiment of this invention, the reflecting region is amultilayer dielectric coating or a multilayer polymeric reflector filmsuch as described in U.S. Pat. Nos. 7,038,745, 6,117,530, 6,829,071,5,825,543, and 5,867,316, the contents of each are incorporated byreference herein, or DBEF film produced by 3M. Multilayer polymericreflective films can have specular or diffuse reflectances in thevisible spectrum greater than 98% and thus can be more efficient in anoptical system. The multi-layer polymeric reflector film may bespecularly reflective, diffusely reflective, diffusely transmissive,anisotropically forward scattering or anisotropically backwardscattering for one or more polarization states. In a backlight where thelight reflecting regions are a multi-layer polymeric reflector, the lowlight loss enables more reflections before the light is absorbed andthus a cavity within the backlight can be made thinner and/or the lighttransmitting apertures can be smaller, thus providing higher uniformityand more light filtering in a thinner form factor.

In a further embodiment, a backlight comprising a light recyclingdirectional control element further comprises red, green, and blue LED'ssuch that the color of the light output can be adjusted to match adesired white point color and color gamut or be used in a color (orfield sequential) display such that the color filters are not required.

Light Absorbing & Light Transmitting Region

In one embodiment of this invention, the light recycling directionalcontrol element comprises light absorbing and light transmitting regionsdisposed substantially in-between light transmitting apertures within alight transmitting layer. Some methods of manufacturing limit thediffuse reflectance of the light reflecting regions to less than 90%.The light transmitted through the reflective regions is less collimatedin some configurations and as a result the angular spread of light maybe larger than desired. In one embodiment of this invention, a lightabsorbing region is disposed between the lenticules and the lightreflecting region substantially over the light reflecting regions. Inthis embodiment, the light absorbing regions will absorb a substantialamount of residual light transmitted through the light reflectingregions. In another embodiment of this invention, the light reflectinglayers reflect a portion of incident light such that the uniformity ofthe incident light pattern is increased without absorbing a significantamount of light that would prohibit recycling and increase light output.

In a further embodiment of this invention, a backlight comprising alight recycling directional control element with a light absorbingregion disposed between the lenticules and the light reflecting regionsubstantially over the light reflecting regions such that the angularluminance within a predetermined angular range greater than 10° inangular width within at least one plane is less than 5% that of the peakintensity in the plane. By using a light absorbing region disposed abovethe light reflecting region, the light leaking through the lightreflecting region is absorbed and does not cause stray light andundesired angles. This is useful in applications where low displayluminance in a predetermined angular range is desired such as airplanecockpits (to reduce canopy reflections) or privacy backlights (such asused with ATMs or desired for use on planes).

In a further embodiment of this invention, a backlight comprising alight recycling directional control element with a light absorbingregion disposed between the lenticules and a light reflecting region hasa diffuse reflectance measured from the light exiting surface of thebacklight of less than one selected from the group of 80%, 60%, 40% 30%,20%, 10% and 5%. In a further embodiment of this invention, a backlightcomprising a light filtering collimating lens has a diffuse reflectanceof less than 20% and appears substantially black when viewed in a firstangular range in the off-state and the on-state. In one embodiment ofthis invention, the ambient light reflected from the display is reducedsuch that the display contrast is improved. By employing a lightabsorbing region along with a light reflecting region, the recycling dueto the light reflecting region and the light transmitting aperturesprovides the increased efficiency, uniformity and angular control, whilethe light absorbing regions provide reduced ambient light reflections(and thus improved display contrast) and lower transmittance above thelight reflecting regions which can reduce light levels in thepredetermined angular range.

The diffuse reflectance of the backlight can be measured in a (d/8geometry) using a Minolta CM-508d with the specular component includedand measuring the reflectance from the light exiting surface on thelight exiting side. The forward luminous transmittance of the lightrecycling directional control element used in a backlight can bemeasured by according to ASTM D1003 measured with the light incident onthe diffuse reflecting side of the light recycling directional controlelement. In one embodiment of this invention, a light recyclingdirectional control element has a diffuse reflectance measured on thelight exiting surface of greater than 30% and a forward luminoustransmittance of greater than 50%. In another embodiment of thisinvention, a light recycling directional control element has a diffusereflectance measured on the light exiting surface of greater than 20%and a forward luminous transmittance of greater than 40%. In anotherembodiment of this invention, the optical system efficiency of abacklight incorporating a light recycling directional control element isgreater than 60% as measured comparing the light source flux output andthe flux output of a backlight incorporating the same light source in asufficiently large calibrated integrating sphere.

In one embodiment of this invention, a light recycling directionalcontrol element comprises a light absorbing region disposed between alenticular lens array and a light reflecting region such that theseparation between the light reflecting region and the light absorbingregion is greater than the thickness of the thinner of the two regions.By spatially separating the two regions, the angular output of the lightexiting the light recycling directional control element will have areduced angular width. By separating the light reflecting and lightabsorbing regions they form a parallax barrier which can be used tolimit the angular output without requiring a reduction in aperturewidth.

In a further embodiment of this invention, the focal point of thelenticules is substantially near at least one of the light absorbingregion or the light reflecting region. In a further embodiment, thefocal point is substantially in-between the light absorbing region andthe light reflecting region. By designing the substrate thickness,refractive index, curvature and surface profile of the lenticules suchthat the focal point is located at the midpoint between the lightreflecting and light absorbing regions, the light throughput isoptimized due to the angular spread from the focal point to the lightabsorbing region being equal to the angular spread from the focal pointto the light reflecting region.

In a further embodiment of this invention, the light reflecting regionsand the light absorbing regions are in contact with each other such aswhite ink printed on a cured black ink or a black toner transferred ontoa white toner or a co-extruded polyester film with a black lightabsorbing layer and a white light reflecting layer.

Area Ratios

In one embodiment of this invention, the light recycling directionalcontrol element comprises at least one of light absorbing region withlight transmitting regions and a light reflecting region with lighttransmitting regions. The light transmitting aperture ratio, AR_(T), isthe ratio of the surface area of the light transmitting region to thetotal area of either the light absorbing region or the light reflectingregion plus the area of the light transmitting region. This area ratioaffects the total optical efficiency, angular output, the spatial colorand luminance uniformity, and the angular color and illuminanceuniformity of the light recycling directional control element or abacklight employing the same. For an element comprising a lightreflecting region, the light transmitting aperture ratio, AR_(T) isdefined by the equation:

${AR}_{T} = \frac{A_{T}}{A_{R} + A_{T}}$where A_(T) is the area of the light transmitting region and A_(R) isthe area of the light reflecting region. Similarly, for an elementcomprising a light absorbing region, the ratio of the surface areas is

${AR}_{T} = \frac{A_{T}}{A_{A} + A_{T}}$where A_(T) is the area of the light transmitting region and A_(A) isthe area of the light absorbing region.

For linear lenticular lens arrays and linear light transmittingapertures, the ratio of the areas can also be determined by the ratio ofthe width of the light transmitting aperture to the pitch where thepitch is the width of the light transmitting region plus either thewidth of the light absorbing region or the light reflecting region.

In one embodiment of this invention, a light recycling directionalcontrol element has a small light transmitting aperture ratio andoutputs more collimated light (light with a smaller angular FWHMcross-section of the intensity) within the plane perpendicular to theoutput surface and parallel to the array the lenticular lenses (parallelto the plane comprising the refraction due to the refractive lenses). Ina further embodiment, light recycling directional control element withsmall light transmitting aperture ratios will filter out more spatiallight intensity irregularities (non-uniformities such as blemishes) andwhen the element comprises a light reflecting region, the recycling willimprove the spatial color and luminance uniformity and enable morethinner optical designs of backlights.

In edge-lit backlights, the light extracted near the incident edge isoften much brighter than that at the far edge. In edge-lit LEDbacklights, the same can be true and the regions of the waveguidecorresponding to the regions between the LED's may less bright than theregions closer to the LED's. The type, size, shape, and spatialarrangement of the light extraction features in edge-lit designs istypically adjusted to result in more uniform output from the backlight.Recycling films such as 90 degree prism films, diffusers, lightscattering films, and white reflective films aid the uniformity throughrecycling and scattering, however, for a given size light entrance edge,the fewer the LED's, the more difficult it is to create a spatiallyuniform light extraction profile.

Luminance Mixing Distance (Parallel)

A term that can be used to measure the distance required to mix andextract the light from the waveguide is the Luminance Mixing Distance(LMD). For backlights, it is desirable to have a luminance uniformity ofat least 70%, or more preferably at least 80%. The uniformity(100%*[1−(Lmax−Lmin)/(Lmax+Lmin)]) is measured in the direction parallelto the entrance edge (typically parallel to the LED array) or in thedirection perpendicular to the entrance edge. The LMD_(∥) is thedistance measured from the entrance edge of the waveguide to the pointwhere the linear spatial luminance cross-section on the output surfaceof the backlight along direction parallel to the entrance edge has aluminance uniformity of at least 80%. Secondary optics on the LED's oroptical components such as reflectors, lenticular lens arrays andanisotropic diffusers may be used on the entrance edge to reduce theLMD_(∥). The length in the plane parallel to the entrance edge of theincident light profile which is incident on the edge of a substantiallyplanar waveguide is termed Entrance Source Length (ESL). The EntranceSource Length is defined as the maximum spatial length on the entranceedge surface along a direction parallel to the edge of the waveguideenclosed by the angular FWHM of the intensity profile of the lightincident on the edge. For backlights with a constant LED pitch andconstant intensity profile incident on the edge, the ESL can be measuredfrom the LED pitch, the angular intensity profile from the LED (or LEDplus secondary optics) and the distance from the LED (or LED plussecondary optics) to the edge of the waveguide. A larger ESL will have ahigher luminance uniformity near the edge of the waveguide and thus theLMD_(∥) is reduced. In the case of a multiple-LED edge-lit backlight,the larger the spacing or pitch (P_(L)) between the LED's along one edgeof a backlight, the larger the LMD_(∥) will be for a fixed opticalsystem (same waveguide and optical components). As a result, one metricfor describing the incident light profile on the edge of a waveguide inrelationship to its affect on the uniformity is the Input Light Ratio,ILR, defined as

${ILR} = {\frac{ESL}{P_{L}}.}$Backlights with a small Input Light Ratio will typically require morelight recycling to achieve a fixed LMD_(∥) than a those with a high ILR.In cases where the LED's are spaced from the edge and the input profilesoverlap, the ILR ratio can be greater than 1. In the special case wherea single LED is used, the ILR is the ESL divided by the length of thedimension of the output surface substantially parallel to the entranceedge. In one embodiment of this invention, a light recycling directionalcontrol element comprises a lenticular lens array, a light reflectingregion, and a light transmitting region wherein the ILR is less than oneselected from the group of 1, 0.7, 0.5, 0.3, 0.2 and 0.1. A metric forevaluating the effectiveness of a backlight to mix the light is theSource Adjusted Luminance Mixing Distance (LM_(∥SA)) which adjusts theLMD_(∥) by the Input Light Ratio and is defined as LMD_(∥SA)=LMD_(∥)×ILR

A backlight with a high level of “fast mixing” (mixing the light wellover a short distance from the edge) has a very low LM_(∥SA) and canprovide a smaller form factor (smaller backlight or display bevel oraluminum reflector). These high performance “fast mixing” backlightshave a small LMD_(∥) and a small ILR value and thus a very smallLM_(∥SA). A backlight that has a large LMD_(∥) and a small ILR or asmall LMD_(∥) and a large ILR has an average performance and mediumLM_(∥SA) value. Backlights with a large LMD_(∥) and a large ILR highhave a very large LM_(∥SA) and poor mixing performance. In oneembodiment of this invention, a light recycling directional controlelement comprises a lenticular lens array, a light reflecting region,and a light transmitting region wherein the LM_(∥SA) is less than oneselected from the group of 5 mm, 3 mm, 2 mm, and 1 mm.

Luminance Mixing Distance (Perpendicular)

The luminance of the backlight in the direction perpendicular to theinput edge will typically be very high near the edge and fall-off thefurther the distance from the edge. The luminance mixing distance of abacklight in the direction perpendicular to the input edge, LMD⊥, is thedistance measured along a line on the light emitting surfaceperpendicular to the entrance edge (passing through the midpoint of thelight emitting surface in the direction parallel to the edge) from theentrance edge of the waveguide to the closest point at which theluminance at any further point along the line is within 80% of theaverage of the remaining points along the line within the designedemitting area (such as that corresponding to the display area). In oneexample, if the LED array is on the left side of a backlight, then theLMD⊥ is the distance from the edge of the waveguide to the first pointalong the middle of the backlight where all other points to the rightwithin the design emitting out area are within 80% of the average of theremaining points to the right. Secondary optics on the LED's or opticalcomponents such as reflectors, lenticular lens arrays and anisotropicdiffusers may be used on the entrance edge to reduce the LMD⊥. Thelength in the plane parallel to the entrance edge of the incident lightprofile which is incident on the edge of a substantially planarwaveguide is termed Entrance Source Length (ESL). The Entrance SourceLength is defined as the maximum spatial length on the entrance edgealong a direction parallel to the edge of the waveguide enclosed by theangular FWHM of the intensity profile of the light incident on the edge.For backlights with a constant LED pitch and constant intensity profileincident on the edge, this can be measured from the LED pitch, theangular intensity profile from the LED (or LED plus secondary optics)and the distance from the LED (or LED plus secondary optics) to the edgeof the waveguide. The location, size, spacing, shape, type, etc. of thelight extraction features will have a significant affect on the LMD⊥.

A backlight with a high level of “fast mixing” along a directionperpendicular to the LED array (mixing the light uniformly across thebacklight in a short distance) has a very high LMD⊥. In one embodimentof this invention, a light recycling directional control elementcomprises a lenticular lens array, a light reflecting region, and alight transmitting region wherein the LMD⊥ is less than one selectedfrom the group of 5 mm, 3 mm, 2 mm, and 1 mm.

Color Mixing Distance (Parallel)

As disclosed above in relation to luminance uniformity, one can alsomeasure the performance in terms of color uniformity. For coloruniformity, the Δu′v′ value is measured between all points in thedirection parallel to the entrance edge (typically parallel to the LEDarray) or in the direction perpendicular to the entrance edge. The ColorMixing Distance, CMD_(∥) is the distance measured from the entrance edgeof the waveguide to the point where the color uniformity Δu′v′ is lessthan 0.04 along a cross-section on the output surface of the backlightalong direction parallel to the entrance edge. Similarly, the ColorMixing Distance (Source Adjusted) is defined asCMD_(∥SA)=CMD_(∥)×ILR.

In one embodiment of this invention, a light recycling directionalcontrol element comprises a lenticular lens array, a light reflectingregion, and a light transmitting region wherein the CMD_(∥SA) is lessthan one selected from the group of 5 mm, 3 mm, 2 mm, and 1 mm.

Color Mixing Distance (Perpendicular)

In the direction perpendicular to the entrance edge, the Color MixingDistance, CMD⊥, is the distance measured along a line on the lightemitting surface perpendicular to the entrance edge (passing through themidpoint of the light emitting surface in the direction parallel to theedge) from the entrance edge of the waveguide to the closest point atwhich the color uniformity Δu′v′ at any point further point along theline is less than 0.1 from the remaining points along the line withinthe designed emitting area (such as that corresponding to the displayarea). In one embodiment of this invention, a light recyclingdirectional control element comprises a lenticular lens array, a lightreflecting region, and a light transmitting region wherein the CMD^(⊥)is less than one selected from the group of 5 mm, 3 mm, 2 mm, and 1 mm.

Protective Layer

In one embodiment of this invention, a light recycling directionalcontrol element further comprises a protective layer to protect at leastone of the light reflecting or light absorbing region from beingscratched during assembly or function use in devices such as backlights.The protective layer may be a laminated PET layer adhered using apressure sensitive adhesive, a protective hardcoating such as those usedin the projection screen and polarizer industry or other protectivelayers or coatings known to increase scratch resistance. In oneembodiment of this invention, the protective layer also provides thespacing between the lenticular lens array and a light collimatingelement.

Anisotropic Light-Scattering Regions

The light recycling directional control element may include more thanone anisotropic light-scattering region or layers. In one embodiment ofthis invention, a backlight comprises a light recycling directionalcontrol element with a first input surface disposed to receive light andan first output surface disposed to output light wherein the lightrecycling directional control element collimates the light within afirst plane and the backlight further comprises a light scatteringelement such as an anisotropic light scattering element disposed in theoptical path after the first light output surface with a larger angularFWHM diffusion profile in the first plane than in a second planeorthogonal to the first. In this embodiment, the light filteringcollimating lens filters out the unwanted non-uniformities of theincident light in a very thin profile and substantially collimates theincident light (such as providing an output light with an angular FWHMof less than 10 degrees FWHM in the first output plane). The anisotropicdiffuser can be provided with a range of angles to provide acustomizable light output profile. In one embodiment of this invention,a backlight with an angular FWHM of less than 10 degrees in at least oneoutput plane and an anisotropic light scattering film is provided as akit wherein the combination of the two provides a pre-determined lightoutput profile.

One or more of the diffusing (scattering) regions may have an asymmetricdiffusion profile in the forward (transmission) or backward (reflection)directions. The light recycling directional control element may containvolumetric and surface-relief-based scattering regions that may beasymmetric or symmetric. The scattering regions or layers may beoptically coupled or separated by another material or an air gap. In oneembodiment of this invention, substantially transparent materialseparates two diffusing regions. In another embodiment of thisinvention, the asymmetrically diffusive regions are aligned such thatthe luminance uniformity of a backlight is improved. In anotherembodiment, the spatial luminance profile of a backlight using a linearor grid array of light sources is made substantially uniform through theuse of one or more asymmetrically diffusing regions.

The use of a volumetric anisotropic light scattering region in thebacklight comprising a light recycling directional control elementallows the scattering region to be optically coupled to the light guidesuch that it will still support waveguide conditions. An anisotropicsurface relief scattering region on the surface of the light guide or asurface of a component optically coupled to the light guide willsubstantially scatter light in that region out of the light guide, thusnot permitting spatially uniform out-coupling in the case of scatteringover a significant portion of the light guide surface. Additionally,anisotropic scattering surface relief structures are difficult tomanufacture in large sizes due to complex holographic recordingtechniques required.

In one embodiment of this invention, the light recycling directionalcontrol element comprises an anisotropic light scattering region whereinasymmetrically shaped dispersed phase domains of one polymer withinanother matrix polymer contribute to the anisotropic light scattering.The anisotropic scattering region may be non-polarization dependentanisotropic light scattering (NPDALS) or polarization dependentanisotropic light scattering (PDALS). Backlights with polarized lightoutput can reduce the glare off of surfaces and discussed in U.S. Pat.No. 6,297,906, the contents of which are incorporated herein byreference.

The amount of diffusion in the x-z and y-z planes for the NPDALS orPDALS regions affects the luminance uniformity and the angular lightoutput profiles of the backlight. By increasing the amount of diffusionin one plane preferentially over that in the other plane, the angularlight output from the backlight is asymmetrically increased. Forexample, with more diffusion in the x-z plane than the y-z plane, theangular light output (measured in the FWHM of the intensity profile) isincreased in the x-z plane. The diffusion asymmetry introduced throughone or more of the anisotropic light-scattering regions of the lightrecycling directional control element can allow for greater control overthe viewing angle, color shift, color uniformity, luminance uniformity,and angular intensity profile of the backlight and the opticalefficiency of the backlight. In another embodiment, the amount ofdiffusion (measured as FWHM of the angular intensity profile) varies inthe plane of the diffusing layer. In another embodiment, the amount ofdiffusion varies in the plane perpendicular to the plane of the layer (zdirection). In another embodiment of this invention, the amount ofdiffusion is higher in the regions in close proximity of one or more ofthe light sources.

The birefringence of one or more of the substrates, elements ordispersed phase domains may be greater than 0.1 such that a significantamount of polarization selectivity occurs due to the difference in thecritical angle for different polarization states when this opticallyanisotropic material is optically coupled to or forms part of the lightguide. An example of this polarization selectivity is found in U.S. Pat.No. 6,795,244, the contents are incorporated herein by reference.

Alignment of Major Diffusing Axis in Anisotropic Light Scattering Region

The alignment of the major axis of diffusion in one or more of theanisotropic light-scattering regions may be aligned parallel,perpendicular or at an angle θ₃ with respect to a light source or edgeof the waveguide. In one embodiment, the axis of stronger diffusion isaligned perpendicular to the length of a linear light source in acold-cathode fluorescent edge-lit backlight. In another embodiment ofthis invention, the axis of stronger diffusion is aligned perpendicularto the length of a linear array of LED illuminating the edge ofwaveguide in an edge-lit LED based backlight.

Domain Shape

The domains within one or more light scattering regions may be fibrous,spheroidal, cylindrical, spherical, other non-symmetric shape, or acombination of one or more of these shapes. The shape of the domains maybe engineered such that substantially more diffusion occurs in the x-zplane than that in the y-z plane. The shape of the domains or domainsmay vary spatially along one or more of the x, y, or z directions. Thevariation may be regular, semi-random, or random.

Domain Alignment

The domains within a diffusing layer may be aligned at an angle normal,parallel, or an angle theta with respect to an edge of the diffusinglayer or a linear light source or array of light sources. In oneembodiment, the domains in a diffusing region are substantially alignedalong one axis that is perpendicular to a linear array of light sources.

Domain Location

The domains may be contained within the volume of a continuous-phasematerial or they may be protruding (or directly beneath a partiallyconformable protrusion) from the surface of the continuous-phasematerial.

Domain Concentration

The domains described herein in one or more light-diffusing regions maybe in a low or high concentration. When the diffusion layer is thick, alower concentration of domains is needed for an equivalent amount ofdiffusion. When the light-diffusing layer is thin, a higherconcentration of domains or a greater difference in refractive index isneeded for a high amount of scattering. The concentration of thedispersed domains may be from less than 1% by weight to 50% by weight.In certain conditions, a concentration of domains higher than 50% byvolume may be achieved by careful selection of materials andmanufacturing techniques. A higher concentration permits a thinnerdiffusive layer and as a result, a thinner backlight or light recyclingdirectional control element. The concentration may also vary spatiallyalong one or more of the x, y, or z directions. The variation may beregular, semi-random, or random.

Index of Refraction

The difference in refractive index between the domains and the matrix inone or more of the NPDALS, PDALS or other light scattering regions maybe very small or large in one or more of the x, y, or z directions. Ifthe refractive index difference is small, then a higher concentration ofdomains may be required to achieve sufficient diffusion in one or moredirections. If the refractive index difference is large, then fewerdomains (lower concentration) are typically required to achievesufficient diffusion and luminance uniformity. The difference inrefractive index between the domains and the matrix may be zero orlarger than zero in one or more of the x, y, or z directions.

The refractive index of the individual polymeric domains is one factorthat contributes to the degree of light scattering by the film.Combinations of low- and high-refractive-index materials result inlarger diffusion angles. In one embodiment of this invention, therefractive index difference between the dispersed phase domain and alight transmitting matrix material is greater than one selected from thegroup of 0.03, 0.05, 0.1 and 0.12 in a first domain axis directionwithin a plane parallel to a light transmitting layer such that thedomains and matrix combination for an anisotropic backscattering regiondue to the large refractive index difference. The number of domainswithin the optical path of the incident light will contribute a totalforward or backward scattering property. Generally, the more domains inan optical path, the more light will be scattered backwards. For a lightscattering region comprising a constant average density of domains, athicker light scattering region will backscatter more incident lightthan a thinner light scattering region.

In cases where birefringent materials are used, the refractive indexesin the x, y, and z directions can each affect the amount of diffusion orreflection in the processed material. In some applications, one may usespecific polymers for specific qualities such as thermal, mechanical, orlow-cost, however, the refractive index difference between the materials(in the x, y, or z directions, or some combination thereof) may not besuitable to generate the desired amount of diffusion or other opticalcharacteristic such as reflection. In these cases, it is known in thefield to use small domains, typically less than 100 nm in size toincrease or decrease the average bulk refractive index. Preferably,light does not directly scatter from these added domains, and theaddition of these domains does not substantially increase the absorptionor backscatter.

During production of the light recycling directional control element orone of its regions, the refractive index of the domains or the matrix orboth may change along one or more axes due to crystallization, stress-or strain-induced birefringence or other molecular or polymer-chainalignment technique.

Additive materials can increase or decrease the average refractive indexbased on the amount of the materials and the refractive index of thepolymer to which they are added, and the effective refractive index ofthe material. Such additives can include: aerogels, sol-gel materials,silica, kaolin, alumina, fine domains of MgF2 (its index of refractionis 1.38), SiO2 (its index of refraction is 1.46), AlF3 (its index ofrefraction is 1.33-1.39), CaF2 (its index of refraction is 1.44), LiF(its index of refraction is 1.36-1.37), NaF (its index of refraction is1.32-1.34) and ThF4 (its index of refraction is 1.45-1.5) or the likecan be considered, as discussed in U.S. Pat. No. 6,773,801, the contentsincorporated herein by reference. Alternatively, fine domains having ahigh index of refraction, may be used such as fine particles of titania(TiO2) or zirconia (ZrO2) or other metal oxides.

Other modifications and methods of manufacturing anisotropic lightscattering regions, and light emitting devices and configurationsincorporating anisotropic light scattering elements are disclosed inU.S. Pat. No. 7,278,775, the contents of which are incorporated byreference herein. The modifications and configurations disclosed thereinmay be employed in an embodiment of this invention to create a uniform,efficient backlight comprising a light recycling directional controlelement.

Anisotropic Scattering Region Location

The light recycling directional control element or a backlightcomprising the light recycling directional control element may compriseone or more anisotropic light scattering regions. On or more of theanisotropic light scattering regions may be located with the lenticularlens structure, within the lenticular lens substrate, within the lightabsorbing region, within the light reflecting region, within the lighttransmitting region, within or adhered to the waveguide, between thelight recycling directional control element and the backlight lightoutput surface, between the light recycling directional control elementand the waveguide or between the waveguide and one or more lightemitting sources such as LED's. The anisotropic light scattering regionmay be optically coupled to one or more elements of the light recyclingdirectional control element or one or more elements of the backlight. Inone embodiment of this invention, the anisotropic light scatteringelement is optically coupled to one or more components of the lightrecycling directional control element or the backlight using a lowrefractive index adhesive. In a further embodiment of this invention, alight recycling directional control element comprises an anisotropiclight scattering film optically coupled using a pressure sensitiveadhesive to the apex region of the lenticules such that the anisotropiclight scattering film provides a substantially planar output surfacethat is more resistant to scratches. In one embodiment, the loss of therefractive power at the apex of the lenticules where the pressuresensitive adhesive effectively index matches out the interface increasesthe FWHM angular intensity output in a plane perpendicular to thelenticules by less than one selected from the group of 2 degrees, 5degrees, 10 degrees, or 20 degrees relative to the anisotropic lightscattering film separated from the lenticular lens array by an air gap.

In one embodiment of this invention, a backlight comprises two lightrecycling directional control elements wherein the lenticules arearranged substantially orthogonal to each other. When a backlightcomprises a first light recycling directional control element on theoutput side of the backlight from a second light recycling directionalcontrol element wherein the lenticules are arranged substantiallyorthogonal to each other and the first light recycling directionalcontrol element comprises symmetrically diffuse reflecting region, thereflected light will reflectively scatter in a plane parallel to thelenticules, which increases the angular FWHM output profile in thatplane. In applications where highly collimated backlight output profilesin two orthogonal planes are desired, this increase in the FWHM in aplane relative to the output from the second light recycling directionalcontrol element is undesirable. In one embodiment of this invention, abacklight comprises a first light recycling directional control elementon the output side of the backlight from a second light recyclingdirectional control element wherein the lenticules are arrangedsubstantially orthogonal to each other and the first light recyclingdirectional control element comprises an anisotropically reflectingregion where the major axis of anisotropically backscattered light isoriented in a plane perpendicular to the lenticules of the first lightrecycling directional control element and the reflected light willreflectively scatter in a plane perpendicular to the lenticules of thefirst light recycling directional control element and substantiallymaintain the collimation in the plane parallel to the lenticules.

Backlight Thickness

In one embodiment of this invention, the backlight is a direct-lit type.In another embodiment of this invention, the backlight is an edge-littype which can generally be made thinner than a direct-lit type. In oneembodiment of this invention, the light recycling directional controlelement increases the uniformity, reduces the thickness and providesincreased collimation. In one embodiment of this invention, the lightrecycling and uniformity derived from the light reflecting region andthe spatial filtering from the light transmitting region and lenticularlens array reduces the thickness of an edge-lit backlight. In oneembodiment of this invention, a backlight comprises at least one LEDlight source, a waveguide, and a light recycling directional controlelement and the distance between an outer surface of the waveguide andlight output surface of the backlight is less than one selected from thegroup of 1.5 millimeters, 1 millimeter and 0.5 millimeters.

In a further embodiment of this invention, a backlight comprises a lightrecycling directional control element (comprising the light outputsurface of the backlight), an optical waveguide, and a white diffuselyreflecting film opposite the light output side of the waveguide.

In a further embodiment of this invention, a backlight comprises a lightrecycling directional control element and at least one of the opticalelements, films or waveguides disclosed in an embodiment of U.S. Pat.No. 5,594,830, the contents of which are incorporated by referenceherein.

Other Films and Components

In one embodiment of this invention, a light recycling directionalcontrol element comprises a lenticular lens array, at least one of alight absorbing or light reflecting region designed to direct lightalong a direction such that the light can effectively be coupled outfrom the waveguide spatially such that the uniformity of the lightexiting the element is improved when illuminated from the edge. In oneembodiment of this invention, a light recycling directional controlelement comprises a lenticular lens array optically coupled to at leastone of a light reflecting region with light transmitting apertures or alight absorbing region with light transmitting apertures, where oneregion is optically coupled to a waveguide.

In another embodiment of this invention a backlight comprises a lightrecycling directional control element and at least one additionalcollimating element such as a 90 degree apex angle prismatic film. Bypre-conditioning the light incident on the light recycling directionalcontrol element, more light is transmitted and the FWHM angular outputangles of the backlight along one or more output planes is reducedrelative to a backlight comprising just the light recycling directionalcontrol element. In one embodiment of this invention, a backlightcomprises two crossed 90 degree prismatic collimating films and a lightrecycling directional control element such that the angular width of theFWHM intensity profile within one output plane is less that 15 degrees.In a additional embodiment of this invention, a backlight comprises twocrossed 90 degree prismatic collimating films and a light recyclingdirectional control element such that the angular width of the FWHMintensity profile within one output plane is less that 10 degrees. Inanother embodiment of this invention, a backlight comprises two crossed90 degree prismatic collimating films and a light recycling directionalcontrol element such that the FWHM along one output plane is less than 8degrees. In another embodiment of this invention, a backlight comprisesa light recycling directional control element, a first 90 degreeprismatic collimating film and a second 90 degree prismatic filmproviding brightness enhancement with anisotropic light scattering phasedomains dispersed within the substrate as describe in U.S. patentapplication Ser. No. 11/679,628, the contents of which is incorporatedherein by reference. In this embodiment, the angular width of the FWHMintensity profile within one output plane is less than one selected fromthe group of 8 degrees, 10 degrees, 15 degrees or 20 degrees. In anotherembodiment of this invention, a backlight comprises a 90 degreeprismatic collimating film disposed above a light recycling directionalcontrol element wherein the prisms are oriented substantially orthogonalto the lenticules and further comprises a second 90 degree prismaticfilm disposed on the opposite side of the light recycling directionalcontrol element providing brightness and uniformity enhancement withanisotropic light scattering phase domains dispersed within thesubstrate and a waveguide and at least one light emitting diode. In oneembodiment of this invention, the use of at least one brightnessenhancing or collimating film along with a light recycling directionalcontrol element which comprises a light absorbing region permits morelight to pass through the light recycling directional control elementdue to the more highly collimated incident light profile upon the lightrecycling directional control element. In one embodiment of thisinvention, a light recycling directional control element, or backlightcomprising the same, comprises at least one collimating film selectedfrom the group of BEF, BEF II, BEF III, TBEF, BEF-RP, BEFII 90/24, BEFII 90/50, DBEF-MF1-650, DBEF-MF2-470, BEFRP2-RC, TBEF2 T 62i 90/24,TBEF2 M 65i 90/24, NBEF, NBEF M, Thick RBEF, WBEF-520, WBEF-818,OLF-KR-1, and 3637T OLF Transport sold by 3M, PORTGRAM V7 sold by DaiNippon Printing Co., Ltd., LUMTHRU that sold by Sumitomo Chemical Co.,Ltd. and ESTINAWAVE W518 and W425 DI sold by Sekisui Chemical Co., Ltd.

The backlight may also comprise a light recycling directional controlelement and a light re-directing component that re-directs asubstantially portion of the light into an off-axis orientation. In oneembodiment of this invention, a backlight comprises a light recyclingdirectional control element and a non-symmetrical prismatic film such asa Image Directing Film (IDF or IDFII) or Transmissive Right Angle Film(TRAF or TRAFII) sold by 3M. In one embodiment of this invention, abacklight comprises a light recycling directional control element and anon-symmetrical prismatic film. In one embodiment of this invention, abacklight comprises a light recycling directional control element and asymmetrical prismatic film to re-distribute the light symmetricallyabout an axis such as a prismatic film with a 60 degree apex angle withthe prisms oriented toward the output surface. In other embodiment ofthis invention, a light recycling directional control element, or abacklight comprising the same, comprises a lenticular lens array, alight reflecting region, light transmitting regions, and a linear prismfilm with an apex angle between 45 degrees and 75 degrees where thesubstrate of the linear prism film is coupled directly or throughanother layer to the light reflecting regions with the prisms orientedaway from the lenticules. In another embodiment of this invention, thelinear prism film is a “reverse prism film” such as sold by MitsubishiRayon Co., Ltd. under the trade names of DIA ART H150, H210, P150 andP210, or is a prismatic film of a similar type as disclosed in theembodiments within U.S. Pat. Nos. 6,545,827, 6,151,169, 6,746,130, and5,126,882, the contents of which are incorporated by reference herein.

In one embodiment of this invention, a backlight comprises an LED arrayon a flexible circuit disposed in a circular or arc shape in proximityto a waveguide within a light recycling directional control element oras a separate component from the light recycling directional controlelement. In one embodiment of this invention, a backlight comprises acircular array of LED's on flexible circuit such that the light from theLED's is directed inward toward the center of a circular disc-shapedwaveguide comprising light extraction elements of at least one typeselected from the group of embossed features, laser-ablated features,stamped features, inked surface patterns, injection molded features,etched surface patterns, sand or glass-blasted micro-patterns, uv curedembossing patterns, dispersed phase particle scattering, scattering fromregion comprising beads, fibers or light scattering or diffractingshapes. In one embodiment of this invention, the backlight in theprevious embodiment further comprises a light recycling directionalcontrol element. In this embodiment, the backlight can illuminate acircular display.

One or more elements or films within the backlight or light recyclingdirectional control element may be combined by using adhesives (such aspressure sensitive adhesives), thermally bonding, co-extrusion, insertmolding, and other techniques known to combine two polymeric films orelements. In one embodiment of this invention, a light recyclingdirectional control element comprises an element with surface reliefstructures of a first material with a first refractive index n_(s) thatis at least one of a lenticular lens array and light collimating elementwherein the element is physically coupled to second optical element byusing second material with a second refractive index n_(c) such thatn_(s)−n_(c)>0.01. In this embodiment, the lenticular lens array orcollimating element can be physically coupled to another element whilestill retaining a level of refraction or reflection. In anotherembodiment, the value n_(s)−n_(c) is greater than one selected from thegroup of 0.05, 0.1, 0.2, 0.4 or 0.5. In one embodiment, the lenticularlens array or collimating element is made of a high refractive index UVcurable material (such as known in the optical film industry anddescribed in U.S. Pat. Nos. 6,107,364, 6,355,754, 6,359,170, 6,533,959,6,541,591, 6,953,623 and international patent applicationPCT/GB2004/000667, the contents of each are incorporated by referenceherein.

In one embodiment of this invention, the light recycling directionalcontrol element (or backlight comprising the same) comprises at leastone coating or component selected from the group of anti-reflectioncoating or film, anti-glare film or coating, tinted film or coating,colored coating or tint, light scattering coating or film, hard-coatingor film comprising a hard-coating, housing or element to hold more thanone component together, element to enable rotation or translation of oneor more elements relative to the other.

In another embodiment of this invention, a backlight comprises anelectrical device for controlling the color (such as individuallyadjusting the output from a red, green and blue LED), angular lightoutput profile (such as by moving a lens), direction of the light outputprofile, intensity of the light output, and mode of operation.

Adjustable Light Output Profile

In one embodiment of this invention, at least one of the peak directionor the FWHM of the angular light output profile in one or more outputplanes of a backlight is manually or electronically adjustable byrotating one or more of the light recycling directional control element,prismatic collimating film, moving the position of a light source suchas an LED or non-symmetric prismatic light re-directing film such asImage Directing Film or Transmissive Right Angle Film, both produced by3M. In another embodiment of this invention, the peak direction or theFWHM of the angular light output profile of a backlight comprising anlight recycling directional control element is adjustable electronicallywithout any moving parts by using an electronically reconfigurablediffusing element such as a Polymer Dispersed Liquid Crystal elementwhich can be switched from a substantially diffuse state to asubstantially clear state by the application of an electric voltage inthe regions corresponding to at least one of the light blocking regions,light reflecting regions, light absorbing regions, light transmittingregions, or region above the lenticular lens array of a light recyclingdirectional control element. In one embodiment, the backlight can beelectronically controlled to switch from a light output profile of lessthan 10 degrees FWHM to one that is greater than 40 degrees within atleast one light output plane.

Light Source

The light source used within one embodiment of this invention of abacklight comprising a light recycling collimating element is at leastone selected from the group of fluorescent lamp, cold-cathodefluorescent lamp, compact fluorescent, radiofluorescent, halogen,incandescent, Mercury vapor, sodium vapor, high pressure sodium, metalhalide, tungsten, carbon arc, electroluminescent, LED, OLED, laser,photonic bandgap based light source. In one embodiment of thisinvention, the light source is a transparent OLED such as those producedby Universal Display Corporation. In a further embodiment of thisinvention, at least one of the light transmitting regions comprises aphosphor or phosphorescent material and the light source emits lightcapable of exciting the phosphor. In one embodiment of this invention,the light transmitting region contains at least one phosphor materialsuch that substantially blue or UV light from at least one LED incidenton the phosphor will cause the phosphor to emit light which will besubstantially collimated or directed by the lenticular lens array orbeads. By using a phosphor material in the light transmitting regionswhich will effectively convert the wavelength and transmit light, thebacklight can be made more uniform by light recycling and reflectionfrom the light reflecting regions of a light recycling directionalcontrol element and the output will direction will be efficientlycontrolled. In one embodiment of this invention, a backlight comprisesan organic light emitting diode (OLED) and a light recycling directionalcontrol element where the angular width of the output of the backlightis less than the angular width of the output of the OLED light source.

Method of Manufacturing the Light Recycling Directional Control Element

In one embodiment of this invention, the light recycling directionalcontrol element is manufactured by according to a predetermined designby using traditional manufacturing techniques such as offsetlithography, web printing, letterpress, digital printing, and screenprinting used for lenticular graphics, prints, images and 3D displayssuch as known in the art. Methods of manufacturing lenticular prints aredisclosed in U.S. Pat. Nos. 7,136,185, 5,573,344, 5,560,799 and Ph.D.thesis by Gary Jacobsen for Dissertation Presented to the Faculty of theSchool of Engineering of Kennedy-Western University for the Degree ofDoctor of Philosophy in Engineering Management titled “FIRST NOVELINVENTION OF INLINE WEB FED ROLL PRINT MANUFACTURING PRODUCTION OFANIMATED/THREE DIMENSIONAL IMAGED PRINT PRODUCTS INCORPORATING ADVANCEDLENTICULAR TRANSPARENT SUBSTRATE . . . ITS ADVANTAGES AND THECOMPARISON/CONTRAST ORDER ANALYSIS TO PRIOR U.S.P.T.O. PATENTED ART.”,the contents of each are incorporated by reference herein. Typicallylenticular image prints comprise 2 or more images separated intoalternating strips disposed near the focal point of the lenticularlenses to generate two or more views in a stereoscopic or “flip” orother viewing mode. Similarly, light absorbing strips are printed,adhered, transferred or otherwise formed on the light input side oflenticular lens arrays in the projection screen and display industry.Methods for producing the light absorbing stripes or light absorbingregions within bead-based or lenticular screens are disclosed in U.S.Pat. Nos. 5,870,224, 6,307,675, 6,781,733, 6,829,086, 5,563,738,6,631,030, 5,563,738, 6,896,757, 6,912,089, 5,870,224 and 6,519,087, thecontents of each are incorporated by reference herein. Other methods ofobtaining light reflecting or light absorbing regions on a substrate orsubstantially planar surface of a lenticular lens array include thermaltransfer such as disclosed in U.S. Pat. No. 4,871,609, the contents ofwhich are disclosed herein by reference. The lenticular printmanufacturing or the projection screen manufacturing processes may bealtered or steps may be added to produce a light recycling directionalcontrol element comprised of a lenticular array or array of surfacerelief lenses such as beads, at least one of a light absorbing or lightreflecting region and a light transmitting region. In one embodiment ofthis invention, the light reflecting region is formed with a similarprocess to one of the methods in the aforementioned patents whereinlight absorbing particles such as carbon black are replaced with lightreflecting particles such as BaSO₄ or TiO₂. In one embodiment of thisinvention, a method of producing a light recycling directional controlelement comprises of forming a layer of light reflecting material on asubstrate, subsequently forming a layer of light absorbing material onthe light reflecting material, thermally or optically transferring thelight absorbing and light reflecting material in selected regions fromthe substrate to a substantially planar surface of a lenticular orsurface relief lens array film such that the light absorbing and lightreflecting regions are registered at a predetermined location on thesubstantially planar side of the lens array.

In another embodiment of this invention, a light recycling directionalcontrol element is produced by printing a light absorbing region upon alenticular lens array in a predetermined linear pattern in registrationwith the lenticules and subsequently printing a light reflecting regionin registration and on top of or spaced apart from the light absorbingregion. In another embodiment of this invention, a light recyclingdirectional control element is produced by subsequently coating a lightabsorbing and light reflecting layer on lenticular substrate andsubsequently exposing through the lenticular lens array with infra-redillumination such that the light is focused in regions corresponding tothe focal point of the lenticular lenses such that at least one of thefollowing occur: the bond between the light absorbing region and thesubstrate is broken, the light absorbing material is ablated off of thesubstrate, the light absorbing material and the light reflectingmaterial is ablated off of the substrate. The light reflecting or lightabsorbing regions may comprise compositions such as infra-red absorbingdies, adhesion modifiers, light sensitive adhesion modifiers etc. suchthat the ablation occurs or the bond is broken at a sufficiently lowlaser power without significantly damaging the lenticular lens surfaceor the opposite, substantially planar surface. The IR exposure may befrom a frequency doubled-YAG laser, a CO₂ laser, a bank of collimatedinfra-red heating lamps or other IR light sources that can be collimatedthrough reflective or refractive optics or have a naturally low beamdivergence. In another embodiment of this invention, the lighttransmitting material used for the lenticules has a light transmissiongreater than one selected from the group of 50%, 60%, 70%, 80% and 90%at the wavelength used for the exposure process.

In a further embodiment of this invention, a method of producing a lightrecycling directional control element comprises forming a layer of lightreflecting material on a substrate, subsequently disposing a layer oflight absorbing material above the light reflecting material, depositingan array of spherical or substantially spherical beads of a diameterthat is at least twice as thick as the combined light reflective andlight absorbing regions, and applying pressure to the beads andsubstrate through the use of stamps, presses, rollers or films onrollers such that the beads are pressed into the light absorbing andlight reflecting regions, wherein one or more of the beads is insufficiently close proximity to the substrate to provide a lighttransmitting aperture. In a further embodiment of this invention, thelight transmitting aperture provided by the bead permits at least 20% ofthe incident light from the bead side to transmit through the lightrecycling directional control element. In a further embodiment of thisinvention, the method of manufacturing a light recycling directionalcontrol element further comprises and additional step of thermal,optical, evaporative, or radiation curing which substantially increasesthe bonding or substantially fixes the location of one or more of thebeads. In one embodiment of this invention, the exposed bead side of thelight recycling directional control element is further coated with asubstantially conformal (or low refractive index) protective sealant andcured (thermally, optically, evaporative, radiation, extrusion coated,etc) such that beads are substantially fixed in their location.

In a further embodiment of this invention, the light recyclingdirectional control element is produced by optically coupling in one ormore regions a lenticular or bead-based surface refractive element to atleast one of a light absorbing and light reflecting region, and furtheroptically coupling the combined element to at least one of a lightcollimating film, a prismatic refractive or total internal reflectionbased film such as a “reverse prism” type film described in U.S. Pat.No. 5,126,882 or IDF or TRAF manufactured by 3M, a symmetrically oranisotropically scattering volumetric or surface relief diffuser, or awaveguide.

In a further embodiment of this invention, a method of producing a lightrecycling directional control element comprises forming a layer of lightreflecting material on a lenticular lens substrate or layer formedthereupon, exposing the light reflecting region with electromagneticradiation wherein the light reflecting layer is altered to form lighttransmitting regions in the areas of higher exposure by the process ofthe voided reflecting materials being heated to a temperature above it'sglass transition temperature and the voids collapse, thus increasing thetransmission in the region. In a further embodiment, heat is applied tothe light reflecting region before or during exposure such that thelight exposure required is reduced. Materials suitable to change theirtransmission due to collapsing voids due to heat or pressure aredescribed in U.S. patent application Ser. No. 10/984,390, the contentsare incorporated herein by reference. In a further embodiment of thisinvention the method of manufacturing a light recycling directionalcontrol element comprises the step of applying pressure to a lenticularlens element with a light reflecting layer disposed on the opposite sideor a layer thereupon of the lenticular lens element than the lenticulessuch that a sufficient amount of pressure is transferred to the voidedlight reflecting region to collapse one or more voided regions disposedbeneath the apex of the lenticules. In a further embodiment, theresulting light filtering optical element of the previous embodiment hasa light transmission greater than 20% in the case of light entering thelenticule side as measured according to ASTM D1003. In a furtherembodiment, heat is applied to the lenticular lens element during orbefore the application of the pressure in the aforementioned embodiment.

In a further embodiment of this invention, a method of producing a lightrecycling directional control element comprises forming or adhering amulti-layer polymeric reflector film on a lenticular lens substrate orlayer formed thereupon, exposing the multi-layer polymeric reflectorwith electromagnetic radiation wherein the light reflecting layer isaltered to form light transmitting regions in the areas of higherexposure. In this embodiment, the light reflecting regions may be mademore transmissive by the process of annealing (changing the refractiveindex in one or more directions in one or more layers or regions,ablation (removing one or more layers or regions), swelling or shrinking(expansion or shrinking in the thickness direction of one or more layersor regions such that the wavelengths corresponding to opticalinterference are shifted closer to the infra-red or UV wavelengthspectrum), or deforming (heating the region to a temperature above it'sglass transition temperature. Simultaneously applied pressure or heatingmay be used with one or more of the embodiments described herein formaking a light recycling directional control element so as to providethe benefit of at least one of increasing the transmittance in theregion, increasing production (or modification) speed, or enable themodification to occur with a lower light intensity such as providing abias temperature for melting or deforming

In another embodiment of this invention, a method of manufacturing alight recycling directional control element comprises the steps ofcoating beads onto voided light reflecting film such as described hereinin the aforementioned voided film patents, applying heat and pressure tothe resulting film such that the beads penetrate into the lightreflecting film and collapse the voids and decrease the distance betweenthe opposite surface to the beads. In a further embodiment, theresulting light filtering optical element of the previous embodiment hasa light transmission greater than 20% in the case of light entering thebead side as measured according to ASTM D1003. By using glass beads orbeads made from cross-linked materials, the deformation temperature canbe selected to be sufficiently greater than the voided material suchthat when pressure or pressure and heat are applied, the beads willdisplace the matrix material of the voided film and/or collapse thevoids in the voided material. In a further embodiment of this invention,the voided film used in the reflective region is one selected from thegroup of a biaxially oriented PET film, a biaxially orientedpolypropylene and a PTFE film.

In a further embodiment of this invention, the method of producing alight recycling directional control element comprises the step oftransferring a light reflecting region onto the substantially planarside of a lenticular lens sheet or layer thereupon by registering andlaser printing or using another electrostatic imaging process using awhite scattering toner such as produced by Automatic Transfer Inc or isdescribed in U.S. Pat. Nos. 4,855,204, 6,114,077, 6,921,617, and6,797,447, the contents of which are incorporated by reference herein.

In one embodiment of this invention, the process of producing a lightrecycling directional control element comprises the step of extrusionembossing (or UV cured embossing) onto or into a light scattering film alenticular or other lens pattern. In this embodiment, the thickness ofthe light recycling directional control element is reduced since thelight scattering film serves as a substrate of the lenticular lensarray. In designs where the light scattering region is disposed betweenthe lenticules and at least one of the light absorbing region and lightreflecting region, the total thickness of the light recyclingdirectional control element is reduced. In one embodiment of thisinvention the process of producing a light recycling directional controlelement comprises extrusion embossing lenticular lens elements onto ananisotropic light scattering diffuser. The features maybe extrusionembossed into the light scattering film during the production of thelight scattering film or as a subsequent step where the features areembossed directly into a region of the light scattering film (includingcapping or outer regions of sufficient thickness) or a coating appliedto the surface of the light scattering film. In another embodiment ofthis invention, the process of producing a light recycling directionalcontrol element comprises the step of extrusion embossing (or UV curedembossing) onto or into a light scattering film a lenticular or otherlens pattern on one or both sides of a light scattering region or film.

In one embodiment of this invention, the process of producing a lightrecycling directional control element comprises the step of applying aUV sensitive material (such as Cromalin by DuPont) to the substantiallyplanar side of a lenticular lens or layer thereupon, exposing throughthe lenticules with substantially collimated UV light incidentsubstantially normal to the array of lenticules, applying lightabsorbing or reflecting particles or toner to the UV sensitive materialwhereupon the exposed regions are less tacky and the particles do notadhere to the UV sensitive materials in the region. In a furtherembodiment of this invention, the process of producing a light recyclingdirectional control element comprises the step of applying a UVsensitive material to the substantially planar side of a lenticular lensor layer thereupon, exposing through the lenticules with substantiallycollimated UV light incident at an angle β₂ from a surface normal to thearray of lenticules, applying light absorbing or reflecting particles ortoner to the UV sensitive material whereupon the exposed regions areless tacky and the particles do not adhere to the UV sensitive materialsin the region. In one embodiment of this invention, β₂ is greater thanone selected from the group of 5 degrees, 10 degrees, 20 degrees, 30degrees, and 45 degree. By exposing through the lenticules at an angle,the resulting spatial locations of the linear light transmitting regionsare displaced relative to UV exposure normal to the array of lenticulesand the resulting light recycling directional control element has anangular light output profile wherein the peak is at an angle β₃ from thenormal to the output surface where β₃>0 degrees such that the peakintensity of the output light is off-axis.

In a further embodiment of this invention, the method of producing alight recycling directional control element comprises the step of usinga white transfer pigment layer for the light reflecting region on alenticular lens film such as described in U.S. Pat. No. 5,705,315. Otherprinting and transfer methods known in the printing industries may alsobe used.

FIG. 1 illustrates one embodiment of this invention of an opticalelement 100 wherein a first portion of incident light 105 passes throughthe light transmitting regions 104 and a second portion 106 of incidentlight is absorbed in the light absorbing regions 103. The light passingthrough the lenticular substrate 102 and the lenticules 101 has anangular FWHM of a measured from the normal to the light recyclingdirectional control element 100. After refraction from the lenticules101, the output light 107 is more collimated. The angular FWHM of thelight 109 emitted from the optical element 100 has an angular FWHM of βin the plane perpendicular to the lenticules where β<α.

FIG. 2 illustrates an embodiment of this invention of a light recyclingdirectional control element 200 wherein a first portion of incidentlight 105 passes through the light transmitting regions 104 and a secondportion 106 of incident light is reflected and scattered from the lightreflecting regions 201 in the light transmitting layer 202. The lightpassing through the lenticular substrate 102 and the lenticules 101 hasan angular FWHM of a measured from the normal to the light recyclingdirectional control element 200 in the plane perpendicular to thelenticules. After refraction from the lenticules 101, the output light107 is more collimated. The angular FWHM of the light 109 emitted fromthe light recycling directional control element 100 has an angular FWHMof β in the plane perpendicular to the lenticules where β<α.

FIG. 3 illustrates another embodiment of this invention of a lightrecycling directional control element 300 wherein a first portion ofincident light 105 passes through the light transmitting regions 104 ina light reflecting region 302 and a light blocking region 301. The lightblocking region may a light absorbing region or a light reflectingregion such that it prevents a first portion of light from transmittingthrough the region. A second portion 106 of incident light is reflectedand scattered from the light reflecting regions 302. The light passingthrough the lenticular substrate 102 and the lenticules 101 has anangular FWHM of a measured from the normal to the light recyclingdirectional control element 300 in the plane perpendicular to thelenticules. After refraction from the lenticules 101, the output light107 is more collimated. The angular FWHM of the light 109 emitted fromthe light recycling directional control element 100 has an angular FWHMof β in the plane perpendicular to the lenticules where β<α. Externallight 108 incident upon the light recycling directional control element300 from the side of the lenticules 101 passes through the lenticules101 and the lenticular substrate 102 and is absorbed in the lightblocking region 301. In another embodiment of this invention, theportion of incident light on the light reflecting region side of thelight recycling directional control element which is not reflected issubstantially absorbed by the light absorbing region.

FIG. 4 illustrates another embodiment of this invention of a lightrecycling directional control element 400 wherein a first portion ofincident light 105 passes through the light transmitting regions 104 ina light reflecting region 302 and a light blocking region 301 and isscattered anisotropically in a plane parallel to the lenticules 101 byasymmetrically shaped dispersed phase domains 401 within the lenticularsubstrate 102. The light passing through the lenticular substrate 102and the lenticules 101 has an angular FWHM of α measured from the normalto the light recycling directional control element 400 in the planeperpendicular to the lenticules. After refraction from the lenticules101, the output light 107 is more collimated. The angular FWHM of thelight 109 emitted from the light recycling directional control element100 has an angular FWHM of β in the plane perpendicular to thelenticules where β<α. A second portion 106 of incident light isreflected and scattered from the light reflecting regions 302. Externallight 108 incident upon the light recycling directional control element400 from the side of the lenticules 101 passes through the lenticules101 and the lenticular substrate 102 and is absorbed in the lightblocking region 301. In another embodiment of this invention, theportion of incident light on the light reflecting region side of thelight recycling directional control element which is not reflected issubstantially absorbed by the light absorbing region.

FIG. 5 illustrates another embodiment of this invention of a lightrecycling directional control element 500 comprising a lighttransmitting layer 507 comprising light transmitting regions 104 andanisotropically backscattering regions 506. A first portion of incidentlight 105 passes through the light transmitting regions 104. The lightpassing through the lenticular substrate 102 and the array of lenticularlenses 101 has an angular FWHM of α measured from the normal to thelight recycling directional control element 500 in the planeperpendicular to the array of lenticular lenses 101 oriented along afirst axis 505 parallel to the y direction. After refraction from arrayof lenticular lenses 101, the output light 107 from the output surface504 is more collimated. The angular FWHM of the light 109 emitted fromthe light recycling directional control element 500 has an angular FWHMof β in the plane perpendicular to the lenticules where β<α. A secondportion 502 of light 106 incident on the input surface 503 isanisotropically scattered back from the anisotropically backscatteringregions 506 comprising asymmetrically shaped dispersed phase domains501. External light 108 incident upon the light recycling directionalcontrol element 500 from the side of the array of lenticular lenses 101passes through the array of lenticular lenses 101 and the lenticularsubstrate 102 and is absorbed in the light blocking region 301.

In another embodiment of this invention, the portion of incident lighton the light reflecting region side of the light recycling directionalcontrol element which is not reflected is substantially absorbed by thelight absorbing region. In a further embodiment of this invention, thelight reflecting region reflectively scatters light anisotropically intoa larger angular FWHM in the plane perpendicular to the lenticules thanparallel to the lenticules due to scattering from the asymmetricallyshaped disperse phased domains oriented with their larger axissubstantially parallel to the lenticules. By reflectively scattering thelight more in the plane perpendicular to the lenticules, the light willmore likely reach a neighboring light transmitting region through fewerbounces and reflections from the light reflecting region. Since thelight reflecting region is less than 100% reflective and some light iseither absorbed in the light reflecting region or passes through (intoundesirable angles or into a light absorbing region where it can beabsorbed), it is desirable for the light to travel through the waveguidesuch that it will reach a neighboring aperture through a minimal numberof reflections from the light reflecting region.

In one embodiment of this invention, a light recycling directionalcontrol element comprises a lenticular lens array and a light reflectingregion comprising asymmetrically shaped disperse phase domains thatreflectively scatter anisotropically such that the angular FWHM of thelight scattering in the plane perpendicular to the lenticules is greaterthan the angular FWHM of the light parallel to the lenticules, and lighttransmitting regions disposed near the focus of the lenticules such thatlight transmitted through the light transmitting apertures has a smallerangular FWHM than the light incident on the light recycling directionalcontrol element. In a further embodiment, a backlight comprises thelight recycling directional control element of the previously describedembodiment.

FIG. 6 illustrates another embodiment of this invention of a lightrecycling directional control element 600 wherein a first portion ofincident light 105 passes through the light transmitting regions 104 ina light reflecting region 302 and a light blocking region 301. The lightpassing through the lenticular substrate 102 and the lenticules 101 hasan angular FWHM of a measured from the normal to the light recyclingdirectional control element 600 in the plane perpendicular to thelenticules. After refraction from the lenticules 101, the output light107 is more collimated and passes through an adhesive layer 604 and aanisotropic light scattering region 602 comprising asymmetrically shapeddispersed phase domains. Passing through the anisotropic lightscattering region 602 the light 601 is scattering into a larger angularFWHM in a plane parallel to the lenticules. The angular FWHM of thelight 109 emitted from the light recycling directional control element100 has an angular FWHM of β in the plane perpendicular to thelenticules where β<α. A second portion 106 of incident light isreflected and scattered from the light reflecting regions 302. Externallight 108 incident upon the light recycling directional control element600 from the side of the lenticules 101 passes through the anisotropiclight scattering region 602, the lenticules 101 and the lenticularsubstrate 102 and is absorbed in the light blocking region 301. Inanother embodiment of this invention, the light recycling directionalcontrol element 200 of FIG. 2 may be used in the configuration of FIG.6.

FIG. 7 illustrates another embodiment of this invention of a backlight700 comprising the light recycling directional control element 300 ofFIG. 3 wherein light 706 emitted from a linear array of LEDs 702 entersa waveguide 703 and is redirected through scattering from a whiteprinted dot light extraction feature 704 such that a portion of thelight 107 passes through the light recycling directional control element300. A second portion 705 of the light reflected or scattered from thelight extraction feature 704 is reflected and scattered from the lightreflecting regions of the light recycling directional control element300. The angular FWHM of the light 701 emitted from the backlight 700has an angular FWHM of φ in the plane perpendicular to the lenticules ofthe light recycling directional control element 300 where φ<α. Inanother embodiment of this invention, the light recycling directionalcontrol element 200 of FIG. 2 may be used in the configuration of FIG.7.

In one embodiment of this invention, a backlight comprises a lineararray of LED's illuminating a waveguide from a least two opposing sidesof a waveguide through the edges. In another embodiment of thisinvention a light recycling directional control element comprises alenticular lens array disposed on a substrate, light reflecting regionsdisposed on the other side of the substrate than the lenticules, lighttransmitting regions disposed to filter and transmit a portion of lightincident to the lenticular lens array from the light reflection regionside and a waveguide wherein the light reflecting region is adhered tothe waveguide and the waveguide comprises at least one selected from thegroup of light extraction features, an anisotropic light scatteringregion, and a spatially modified reflective region (departure in one ormore regions from a regular linear array of clear apertures to an arrayof dots for example) to provide increased uniformity and lightextraction from the waveguide. In one embodiment of this invention, abacklight comprises a light recycling directional control elementcomprising a reflective region that defines light transmitting aperturesthat vary in length and width in the directions parallel andperpendicular to the lenticules and are disposed substantially near theoptical axes of the lenticules such that the light exits the waveguidethrough the apertures and exits the backlight within an angular FWHM ofless that 70 degrees in at least one output plane.

FIG. 8 illustrates another embodiment of this invention of a edge-litbacklight 800 comprising the light recycling directional control element300 of FIG. 3, an anisotropic light scattering film 802 opticallycoupled to a waveguide 806 and an LED array 807. Light 801 emitted froma linear array of LEDs 807 enters the waveguide 806 and isanisotropically scattered in a direction parallel to the LED array 807by the asymmetrically shaped dispersed phase domains 803 in theanisotropic light scattering film 802 and redirected through reflectionor scattering from a light extraction features 804 such that a portionof the light 107 passes through the light recycling directional controlelement 300. A second portion 805 of the light reflected or scatteredfrom the light extraction feature 804 is reflected and scattered fromthe light reflecting regions of the light recycling directional controlelement 300. The angular FWHM of the light 701 emitted from thebacklight 800 has an angular FWHM of φ in the plane perpendicular to thelenticules of the light recycling directional control element 300 whereφ<α. In another embodiment of this invention, the light recyclingdirectional control element 200 of FIG. 2 may be used in theconfiguration of FIG. 8.

FIG. 9 illustrates another embodiment of this invention of a direct-litbacklight 900 comprising the light recycling directional control element300 of FIG. 3, an anisotropic light scattering film 902 opticallycoupled to a substrate 907 and an LED array 807. Light 801 emitted froma linear array of LEDs 807 enters the waveguide, a reflective housing906, and an array of substantially parallel cold cathode fluorescentlamps 904 with reflective regions 905 beneath the lamps. A portion ofthe light 107 emitted from the cold cathode fluorescent lamps 904 passesthrough the substrate 907 and is anisotropically scattered in adirection perpendicular to the array of fluorescent lamps 904 by theasymmetrically shaped dispersed phase domains 903 in the anisotropiclight scattering film 902 and passes through the light recyclingdirectional control element 300. A second portion 908 of the light fromthe cold cathode fluorescent lamps passes through the substrate 907 andis anisotropically scattered in a direction perpendicular to the arrayof fluorescent lamps 904 by the asymmetrically shaped dispersed phasedomains 903 in the anisotropic light scattering film 902 and isreflected and scattered from the light reflecting regions of the lightrecycling directional control element 300. The anisotropic lightscattering film efficiently increases the spatial luminance uniformityin the direction perpendicular to the cold cathode fluorescent lamps.The angular FWHM of the light 901 emitted from the backlight 900 has anangular FWHM of φ in the plane perpendicular to the lenticules of thelight recycling directional control element 300 where φ<α. In anotherembodiment of this invention, the light recycling directional controlelement 300 of FIG. 2 may be used in the configuration of FIG. 9. Inanother embodiment of this invention the lenticules are arrangedperpendicular to the cold cathode fluorescent lamps.

In one embodiment of this invention, a direct lit backlight comprises anarray of LED's illuminating a light recycling directional controlelement comprising an anisotropic light scattering region, a lightreflecting region, and an array of lenticular lenses.

FIG. 10 illustrates one embodiment of this invention of a backlight 1000comprising the light recycling directional control element 300 of FIG.3, a light collimating element 1002 with linear prismatic features with90 degree apex angles, a diffuser 1001, a waveguide 703, a whitereflector film 1008, and a linear array of LEDs 702 comprising an arrayof LEDs. Light 706 emitted from the linear array of LEDs 702 enters awaveguide 703 and is redirected through scattering from a white printeddot light extraction feature 704 such that a portion of the light 1006passes through the diffuser 1002, the light collimating element 1002 andthe light recycling directional control element 300. A portion of light1005 is scattered from the white printed dot light extraction feature704 is scattered by the diffuser 1001, and is re-directed by thecollimating element 1002 and is reflected by the light reflecting regionin the light recycling directional control element 300. Light 1003 isscattered from the white printed dot light extraction feature 704 and aportion of this light 1004 is reflectively scattered by the diffuser1002. A second portion of the light 1007 that is scattered from thewhite printed dot light extraction feature 704 and the diffuser 1001totally internally reflects (TIR) and is redirected back to thewaveguide. A portion of the light 1004 scattered from the extractionfeatures 704 is reflectively scattered from the diffuser 1001 back intothe waveguide 703. The light recycling directional control element 300comprises a lenticular lens array surface of a first pitch P1 and thelight collimating element has a second pitch P2. In one embodiment ofthis invention, P2/P1=1/(N+0.5) where N is an integer. The lightrecycling directional control element of this invention can achievehigher level of collimation (smaller angular FWHM) than a prismatic filmsuch as a light collimating prismatic film with 90 degree apex angles.Light oriented at large angles to the light recycling directionalcontrol element has a lower percentage chance of passing through thelight transmitting regions because of the finite thickness of at leastone of the light absorbing and light reflecting regions. By reducing theangular FWHM of the light incident on the light recycling directionalcontrol element the throughput is higher and the optical flux output isgreater. One technique for reducing the angular FWHM of the lightincident on the light recycling directional control element is to use alight collimating element such as a 90 degree linear prismatic film withthe prisms oriented substantially parallel to the lenticules. In oneembodiment of this invention, a backlight comprises a light recyclingdirectional control element and a “reverse prism” film is disposedbetween the light reflecting regions and a waveguide with the prismsoriented toward the waveguide in order to produce a more collimatedinput to the light recycling directional control element.

FIG. 11 illustrates one embodiment of this invention of a method forproducing the light recycling directional control element 300 of FIG. 3.A lenticular lens film 1100 is coated with a thin layer of a lightabsorbing material 1101 such as carbon black particles dispersed in a UVcurable or evaporative based (solvent cured) ink. After curing the lightabsorbing material 1101 a thin layer of a light reflecting material 1102such as barium sulfate particles dispersed in a UV curable orevaporative based (solvent cured) ink is coated on the light absorbingmaterial 1101. Substantially collimated infra-red light 1103 from afrequency-doubled YAG laser is directed through the lenticular and nearthe focal regions such that the intensity of the irradiation issufficient enough to ablate the light absorbing material from thelenticular substrate and carry the corresponding light reflecting regionfrom it, thus creating light transmitting regions 1104.

FIG. 12 illustrates another embodiment of this invention of a backlight1200 comprising a light recycling directional control element 1206wherein a first portion of incident light 1201 emitted from a lineararray of LEDs 1212 is scattered from a light extraction feature 704 andpasses through the light transmitting regions 1208 in a light reflectingregion 1207 and a light absorbing region 1208. The light transmittingregions 1208 are disposed such that they are substantially centeredin-between the lenticules 1210. A second portion 1211 of incident lightis scattered from the extraction feature 704 reflected and scatteredfrom the light reflecting regions 1207. The light passing through thelenticular substrate 1209 and the lenticules 1210 is refracted by thelenticules 1210 such that it is separated into light 1205 traveling at afirst peak luminance angle 1213 and light 1204 traveling at a secondpeak luminance angle 1214 from a normal 1215 to the light transmittingregion. The two angular luminance peaks are the result of the positionof the light transmitting regions relative to the lenticules. In afurther embodiment of this invention, a display incorporating thebacklight 1200 can be readily view from two directions with a higherluminance than that at an angle normal to the display.

In some embodiments of this invention, the light recycling directionalcontrol element permits the thickness of the light emitting devicerelative to the width of the device to be reduced. In some embodimentsof this invention, the thickness of the light emitting device comprisinga light recycling directional control element can be reduced relative tothe distance, L. In a further embodiment of this invention, the lightemitting device has a width, w, such that

$\frac{w}{t} > {5\mspace{14mu}{or}\mspace{14mu}\frac{w}{t}} > {10\mspace{14mu}{or}\mspace{14mu}\frac{w}{t}} > 20.$In a further embodiment of this invention

$\frac{L}{t} > {5\mspace{14mu}{or}\mspace{14mu}\frac{L}{t}} > {10\mspace{14mu}{or}\mspace{14mu}\frac{L}{t}} > {20\mspace{14mu}{or}\mspace{14mu}\frac{L}{t}} > 50.$

FIG. 13 illustrates another embodiment of this invention of a display1300 incorporating the backlight 1000 of FIG. 10 wherein the output 1006from the backlight 1000 passes through a liquid crystal display panel1301 and the resulting angular light output 1303 is substantiallycollimated such that the angular FHWM 1302 of the angular luminanceprofile in the plane parallel to the array of lenticules is less than 40degrees. In one embodiment of this invention, the display panel 1301 maybe a liquid crystal display panel. In a further embodiment of thisinvention, the display is a sign and the display panel is a lighttransmissive graphic, image, text or other indicia panel such as usedwith backlit signs. In this embodiment, the light recycling directionalcontrol element can direct the light output into primarily thedirections where it is likely to be viewed, thus increasing thebrightness or reducing the power requirements. In a further embodimentof this invention, a sign comprises the light recycling directionalcontrol element of FIG. 2 wherein the light output is substantiallycollimated for when the sign is in emissive mode and the ambient lightreflects off the light reflecting region in a daylight (or non-emissive)mode. In one embodiment the reflectance of the light reflecting regionsis greater than 50% and the sign has a high luminance due to reflectedambient light.

FIG. 14 illustrates another embodiment of this invention of an opticalelement 1400 which recycles and controls the direction of light. Theoptical element 1400 comprising a light transmitting layer 1404comprising light transmitting regions 104 and anisotropicallybackscattering regions 506. A first portion of incident light 105 passesthrough the light transmitting regions 104 in the light transmittinglayer 1404. The light 107 passing through the lenticular substrate 102and the lenticular elements 1405 has an angular FWHM of α measured fromthe normal to the light recycling directional control element 1400 inthe plane perpendicular to the lenticular elements 1405 oriented along afirst axis 505 parallel to the y direction. After refraction from thelenticular elements 1405, the output light 107 from the output surface504 is more collimated. The angular FWHM of the light 109 emitted fromthe optical element 1400 has an angular FWHM of β in the planeperpendicular to the first axis 505 where β<α. A second portion 1402 oflight 106 incident on the input surface 503 is anisotropically scatteredback from the anisotropically backscattering regions 506 comprisingasymmetrically shaped dispersed phase domains 501 oriented parallel tothe first axis 505. The anisotropically backscattered light 1402 has alarger angular FWHM intensity in the x-z plane than in the y-z plane.External light 108 incident upon the optical element 1400 from the sideof the lenticular elements 1405 passes through the lenticular elements1405 and the lenticular substrate 102 and is anisotropically scatteredback toward the lenticular elements 1405.

FIG. 15 illustrates another embodiment of this invention of a lightrecycling directional control element 1500 comprising a lighttransmitting layer 1404 comprising light transmitting regions 104 andanisotropically backscattering regions 506. A first portion of incidentlight 105 passes through the light transmitting regions 104 in the lighttransmitting layer 1404. The light 107 passing through the lenticularsubstrate 102 and the lenticular elements 1405 has an angular FWHM of αmeasured from the normal to the light recycling directional controlelement 1400 in the plane perpendicular to the lenticular elements 1405oriented along a first axis 505 parallel to the y direction. Afterrefraction from the lenticular elements 1405, the output light 107 fromthe output surface 504 is more collimated. The angular FWHM of the light109 emitted from the light recycling directional control element 1500has an angular FWHM of β in the plane perpendicular to the first axis505 where β<α. A second portion 1402 of light 106 incident on the inputsurface 503 is anisotropically scattered back from the anisotropicallybackscattering regions 506 comprising asymmetrically shaped dispersedphase domains 501 oriented parallel to the first axis 505. Theanisotropically backscattered light 1402 has a larger angular FWHMintensity in the x-z plane than in the y-z plane. External light 108incident upon the light recycling directional control element 1500 fromthe side of the lenticular elements 1405 passes through the lenticularelements 1405 and the lenticular substrate 102 and is absorbed in thelight blocking region 301.

FIG. 16 illustrates another embodiment of this invention of a lightrecycling directional control element 1600 comprising the opticalelement 1400 of FIG. 14. The light recycling directional control element1600 further comprises a second group of lenticular elements 1608coupled to the optical element 1400. The second group of lenticularelements 1608 are oriented substantially parallel to a second axis 1609which is orthogonal to the first axis 505 of the optical element 1400. Afirst portion of light 105 incident on the input surface 1612 passesthrough the second light transmitting regions 1602 in a second lighttransmitting layer 1601.

The light 1611 passing through second light transmitting regions 1602 inthe second light transmitting layer 1601 and the second lenticularsubstrate 1607 is redirected by the second group of lenticular elements1608 toward the optical element 1400 and is more collimated in the y-zplane. Light 105 incident on the optical element 1400 is furthercollimated in the x-z plane. The light 109 having passed through thelight recycling directional control element 1500 comprising the opticalelement 1400 is collimated in two orthogonal planes. The angular FWHM ofthe light 109 emitted from the light recycling directional controlelement 1400 has an angular FWHM of β in the plane perpendicular to thefirst axis 505 where β<α. A second portion of light 1610 incident on theinput surface 1612 is collimated in the y-z plane by the second group oflenticular elements 1608 and is anisotropically scattered back from theanisotropically backscattering regions 506 comprising asymmetricallyshaped dispersed phase domains 501 oriented parallel to the first axis505. A first portion of light 1606 of the light backscattered from theanisotropic backscattering regions 506 is further anisotropicallybackscattered by light reflecting regions 1603 disposed between thesecond light transmitting regions 1602 in the second light transmittinglayer 1601. In one embodiment of this invention, the light reflectingregion comprises asymmetrically shaped dispersed phase domains 1604oriented perpendicular to the first axis 505. In a further embodiment ofthis invention, the light reflecting regions 1603 specularly reflectlight. In the case where the light reflecting regions 1603anisotropically scatter more light in x-z plane and less in the y-zplane (by having a larger and smaller angular FWHM scattering intensityin the corresponding scatter planes) and the case where the lightreflecting regions 1603 specularly reflect light, neither will reducethe collimation that has been gained from the light having passedthrough the second group of lenticular elements 1608 in combination withthe second light transmitting layer 1601. Furthermore, the light willreflect in a cavity-like configuration between the light reflectingregion 1603 and the anisotropic backscattering regions 506 withoutsignificantly spreading further in angle in the y-z plane and a portionof the light will passes through the light transmitting regions of theoptical element 1400, thus maintaining the collimation in the x-z planeand enabling collimation in both the x-z and y-z planes.

FIG. 17 illustrates another embodiment of this invention of a lightrecycling directional control element 1700 comprising an input surface1715, an output surface 1711, a first light transmitting layer 1703, afirst linear array of lenticular elements 1714 oriented parallel to afirst axis 1707 which is parallel to the y direction. The first lineararray of lenticular elements have a first pitch P1. The light recyclingdirectional control element 1700 further comprises a light transmittinglayer 1703 comprising first light reflecting regions 1706 disposedin-between the first light transmitting regions 1705, and a lightcollimating element 1701 comprising a linear array of light redirectingfeatures 1716 oriented substantially parallel to the first axis 1707with a second pitch P2. A first portion of incident light 1708 travelsthrough the light transmitting regions 1705 and is redirected to anangle θ of peak luminance from the normal 1712 to the first lighttransmitting layer 1703. In one embodiment of this invention, θ isbetween 20 degrees and 40 degrees. In a further embodiment of thisinvention,

$\frac{0.9}{N + 0.5} < \frac{P\; 2}{P\; 1} < {\frac{1.1}{N + 0.5}\mspace{14mu}{or}\mspace{14mu}\frac{0.9}{N + 0.5}} < \frac{P\; 1}{P\; 2} < \frac{1.1}{N + 0.5}$where N is an integer such that the luminance contrast of the moiréinterference pattern is between the first linear array of lenticularelements 1714 and the linear array of light redirecting features 1716 inthe light collimating element 1701 is reduced. In one embodiment of thisinvention, the luminance contrast of the moiré pattern is less then oneselected from the group of 30%, 20% and 10%. In one embodiment of thisinvention, the first light transmitting layer is disposed between thelight collimating element and the first linear array of lenticularelements. In a further embodiment of this invention, the first lineararray of lenticular elements 1714 are disposed between the lighttransmitting layer 1703 and the light collimating element 1701. In oneembodiment of this invention, the light recycling directional controlelement 1700 comprises a first linear array of lenticular elementsoptically coupled to the light collimating element at the apexes of thelenticular elements using a pressure sensitive adhesive that issubstantially thinner than the height of the lenticules. By using apressure sensitive adhesive that it substantially thinner than theheight of the lenticules, the refractive power lost due to therefractive index match at the interface between the lenticules and thepressure sensitive adhesive is minimized. In one embodiment, theadhesive thickness is less than 30% of the height of the lenticules. Inanother embodiment, the adhesive thickness is less than 20% of theheight of the lenticules. The light collimating film 1701 may beoptically coupled to an optical element 1702 comprising a linear arrayof lenticular lenses 1714 by using a low refractive index region such asa fluorinated adhesive, a fluoropolymer region, or other suitable lowrefractive index region such as discussed herein and in the patentapplications referenced herein and known in the industry. This regionmay be in the form of an adhesive, co-extruded layer, have tie oradhesion promoting surfaces or layers, injection molded layer, or otherform suitable for providing a low refractive index material such that itis substantially conformal to the linear array of lenticular lenses. Ina further embodiment of this invention, the first group of lenticularelements and the light collimating element have a pitch combinationselected from the group P1 is between 180 μm and 195 μm and P2 isbetween 20 μm and 30 μm, P1 is between 415 μm and 435 μm and P2 isbetween 40 and 60 μm, and P1 is between 40 μm and 55 μm and P2 isbetween 350 and 365 μm. In the embodiment depicted in FIG. 17, a secondportion of incident light 1709 will reflect from the light reflectingregions 1706. A third portion of incident light 1710 will totallyinternally reflect from the linear array of light redirecting features1716 and pass back through the first group of lenticular elements 1714.A portion of this reflected light 1713 will reflect from the lightreflecting regions 1706 back toward the light collimating element 1701.

FIG. 18 illustrates another embodiment of this invention of a lightemitting device comprising a light source 1802, a first output surface1711 and a light recycling directional control element 1702 comprising afirst light transmitting layer 1703, a linear array of lenticularelements 1714 formed in a first light transmitting material orientedparallel to a first axis 1707 which is parallel to the y direction. Thefirst linear array of lenticular elements have a first pitch P1. Thelight transmitting layer 1703 comprises first light reflecting regions1706 disposed in-between the first light transmitting regions 1705. Thelight emitting device further comprises a light collimating element 1701comprising a linear array of light redirecting features 1716 orientedsubstantially parallel to the first axis 1707 with a second pitch P2.light 706 from the light source 1802 is directed toward the lightrecycling directional control element. In one embodiment of thisinvention, the light source 1812 is a linear array of LEDs and the lightfrom the LEDs is coupled into the edge of a waveguide 703 wherein lightextraction features 704 in a pattern on the lightguide 703 redirect aportion of light such that it escapes the lightguide 703. A firstportion of light 1708 originating at the light source 1812 travelsthrough the light transmitting regions 1705 and is redirected to anangle θ of peak luminance from the normal 1712 to the first lighttransmitting layer 1703. In one embodiment of this invention, θ isbetween 20 degrees and 40 degrees. In a further embodiment of thisinvention,

$\frac{0.9}{N + 0.5} < \frac{P\; 2}{P\; 1} < {\frac{1.1}{N + 0.5}\mspace{14mu}{or}\mspace{14mu}\frac{0.9}{N + 0.5}} < \frac{P\; 1}{P\; 2} < \frac{1.1}{N + 0.5}$where N is an integer such that the luminance contrast of the moiréinterference pattern is between the first linear array of lenticularelements 1714 and the linear array of light redirecting features 1716 inthe light collimating element 1701 is reduced. In one embodiment of thisinvention, the luminance contrast of the moiré pattern is less then oneselected from the group of 30%, 20% and 10%. In one embodiment of thisinvention, the first light transmitting layer is disposed between thelight collimating element and the first linear array of lenticularelements. In a further embodiment of this invention, the first lineararray of lenticular elements 1714 are disposed between the lighttransmitting layer 1703 and the light collimating element 1701. In oneembodiment of this invention, the light recycling directional controlelement 1700 comprises a first linear array of lenticular elementsoptically coupled to the light collimating element at the apexes of thelenticular elements using a pressure sensitive adhesive that issubstantially thinner than the height of the lenticules. By using apressure sensitive adhesive that it substantially thinner than theheight of the lenticules, the refractive power lost due to therefractive index match at the interface between the lenticules and thepressure sensitive adhesive is minimized. In one embodiment, theadhesive thickness is less than 30% of the height of the lenticules. Inanother embodiment, the adhesive thickness is less than 20% of theheight of the lenticules. The light collimating film 1701 may beoptically coupled to an optical element 1702 comprising a linear arrayof lenticular lenses 1714 by using a low refractive index region such asa fluorinated adhesive, a fluoropolymer region, or other suitable lowrefractive index region such as discussed herein and in the patentapplications referenced herein and known in the industry. This regionmay be in the form of an adhesive, co-extruded layer, have tie oradhesion promoting surfaces or layers, injection molded layer, or otherform suitable for providing a low refractive index material such that itis substantially conformal to the linear array of lenticular lenses. Ina further embodiment of this invention, the first group of lenticularelements and the light collimating element have a pitch combinationselected from the group P1 is between 180 μm and 195 μm and P2 isbetween 20 μm and 30 μm, P1 is between 415 μm and 435 μm and P2 isbetween 40 and 60 μm, and P1 is between 40 μm and 55 μm and P2 isbetween 350 and 365 μm. In the embodiment depicted in FIG. 18, a secondportion of light 1709 originating at the light source 1812 will reflectfrom the light reflecting regions 1706. A third portion of light 1710originating from the light source 1802 will totally internally reflectfrom the linear array of light redirecting features 1716 and pass backthrough the first group of lenticular elements 1714. A portion of thisreflected light 1713 will reflect from the light reflecting regions 1706back toward the light collimating element 1701. In one embodiment ofthis invention, the light emitting device has a peak luminance angle, φ,defined from the normal 1712 to the first light transmitting layer 1703.In one embodiment, φ, is less than 5 degrees. In a further embodiment ofthis invention, the light collimating element 1701 comprises a lineararray of prisms 1716 with an apex angle 1801 between 80 degrees and 110degrees and pitch, P2, between 40 μm and 60 μm.

FIG. 19 illustrates another embodiment of this invention of a display1900 comprising a emitting device 1800 and a liquid crystal displaypanel 1301. The display has a peak luminance angle, φ2, defined from thenormal 1712 to the first light transmitting layer 1703. In a furtherembodiment, φ2, is less than 5 degrees.

Example 1

An optical element is made from a 187 micron lenticular lens array filmprinted on the flat side with linear array of white lines using a lasertransfer process. The white lines were aligned substantially parallel tothe lenticules and in the regions directly beneath the apex of thelenticules. The white lines are approximately 100 μm wide with a pitchof approximately 187 μm. The optical element is positioned above anedge-lit waveguide with light extraction features and a white PET-basedreflector on the opposite side. The light output from the resultinglight emitting device has far-field peak illuminance angles greater than30 degrees from the normal.

Example 2

An optical element is made from a 187 micron lenticular lens array filmlaminated with Cromalin light sensitive film from DuPont Inc. CollimatedUV light from a 1 kW Tamarack UV exposure system is directed to thelenticular film at angle of 15 degrees from the normal to the film suchthat the light passes through the lenticular elements and exposes theCromalin light sensitive film. The protective cover is removed from theCromalin and white titanium dioxide powder is then applied by soft brushto the cromalin film. The film is then blanket UV cured to fully curethe Cromalin. When the optical element is positioned on a diffuser sheetwhich is directly illuminated by LEDs with the light incident on thelight reflecting surface, the far-field peak angle of illuminance is at15 degrees and light is visible in the angular ranges corresponding tolight passing through the white regions.

Example 3

An optical element is made from a 187 micron lenticular lens array filmlaminated with Cromalin light sensitive film from DuPont Inc. CollimatedUV light from a 1 kW Tamarack UV exposure system is directed to thelenticular film at angle of 15 degrees from the normal to the film suchthat the light passes through the lenticular elements and exposes theCromalin light sensitive film. The protective cover is removed from theCromalin and carbon black powder is then applied by soft brush to theCromalin film. The film is then blanket UV cured to fully cure theCromalin. A second layer of Cromalin film is laminated to the firstCromalin film. The optical element is then exposed similarly withcollimated UV light directed at 15 degrees. The protective cover isremoved from the Cromalin and white titanium dioxide powder is thenapplied by soft brush to the second layer of Cromalin film. The film isthen blanket UV cured to fully cure the Cromalin. This resulted in anoptical element with black regions disposed in-between the lenticularelements and the white reflecting regions. When the optical element ispositioned on a diffuser sheet which is directly illuminated by LEDswith the light incident on the light reflecting surface, the far-fieldpeak angle of illuminance is at 15 degrees and light is not visible inthe angular ranges corresponding to light passing through the white andblack regions.

Example 4

An anisotropic backward scattering film is produced by extruding a blendof 70% PETG and 30% LLDPE through a twin screw extruder and stretched inthe MD direction such that diffuser has a backward scattering FWHM of 60degrees by 1 degrees. The anisotropic backscattering film is opticallycoupled to a lenticular lens film with the domains oriented parallel tothe lenticules. Light from a laser with a wavelength of 1064 nm isdirected through the lenticules onto the backscattering film such thatthe focused laser light removes the region of exposure within the film.

Example 4

A 187 micron lenticular lens array film is coated with an acrylate basedlacquer comprising carbon black particles with a mean particle size lessthan 2 μm to a thickness of 5 μm onto a PFA fluoropolymer film toplanarize the coating. The FEP film is removed and a layer of aluminumis vacuum deposited on the acrylate based coating side of the film suchthat the surface has a reflectance greater than 80%. Light from a laserwith a wavelength of 1064 nm is directed through the lenticules onto thelight reflecting region such that it ablates the acrylate based regionand removes the light reflecting coating in the exposed region.

EQUIVALENTS

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, numerous equivalents to thespecific procedures described herein. Such equivalents are considered tobe within the scope of the invention. Various substitutions,alterations, and modifications may be made to the invention withoutdeparting from the spirit and scope of the invention. Other aspects,advantages, and modifications are within the scope of the invention. Thecontents of all references, issued patents, and published patentapplications cited throughout this application are hereby incorporatedby reference. The appropriate components, processes, and methods ofthose patents, applications and other documents may be selected for theinvention and embodiments thereof.

What is claimed is:
 1. An optical element comprising: a) an inputsurface; b) an output surface; c) first light transmitting regions; d)first anisotropically backscattering regions comprising asymmetricallyshaped dispersed phase domains oriented substantially parallel to afirst axis dispersed in a second light transmitting material; e)lenticular elements formed in a first light transmitting materialwherein the lenticular elements comprise at least a first group oflenticular elements oriented parallel to the first axis; f) a lighttransmitting layer disposed in an optical path between the input surfaceand the first group of lenticular elements comprising the firstanisotropically backscattering regions disposed in-between the firstlight transmitting regions; wherein the first anisotropicallybackscattering regions scatter light received from the input surfaceback toward the input surface in a larger angular full-width at halfmaximum intensity in a first plane orthogonal to the input surface andparallel to the first axis than in a second plane orthogonal to thefirst plane.
 2. The optical element of claim 1 wherein the refractiveindex difference between the dispersed phase domains and the secondlight transmitting material is greater than 0.05 in a first domain axisdirection within a plane parallel to the first light transmitting layer.3. The optical element of claim 1 further comprising light blockingregions disposed between the anisotropically backscattering regions andthe first group of lenticular elements with a transmission less than20%.
 4. The optical element of claim 3 wherein the light blockingregions absorb more than 70% of incident light.
 5. The optical elementof claim 3 wherein light blocking regions have a diffuse reflectance,DR, greater than 70% as calculated by${DR} = \frac{DRT}{\left( {1 - {ART}} \right)}$ where DRT is the totaldiffuse reflectance of the optical element measured from the inputsurface in the d/8 geometry with the specular component included and ARTis the percentage area ratio of the total of the first light blockingregions and first light transmitting regions that is occupied by thefirst light transmitting region.
 6. The optical element of claim 3further comprising second anisotropically backscattering regionsdisposed between the light blocking regions and the first group oflenticular elements.
 7. A light emitting device with a substantiallycollimated light output comprising the optical element of claim
 1. 8.The optical element of claim 1 further comprising: a) second lighttransmitting regions; b) second light reflecting regions; c) secondlenticular elements formed in a second light transmitting material; d) asecond group of lenticular elements oriented perpendicular to the firstaxis; e) a second light transmitting layer disposed in an optical pathbetween the second group of lenticular elements and the output surfacecomprising the second light reflecting regions disposed in-between thesecond light transmitting regions; f) wherein the second lightreflecting regions are disposed between the input surface and the firstlight transmitting layer.
 9. A light emitting device with asubstantially collimated light output comprising the optical element ofclaim
 8. 10. An optical element comprising: a) an input surface; b) anoutput surface; c) first light transmitting regions; d) first lightreflecting regions; e) a linear array of lenticular elements formed in afirst light transmitting material; f) a first group of lenticularelements oriented parallel to a first axis with a first pitch P1; g) alight transmitting layer comprising the first reflecting regionsdisposed in-between the first light transmitting regions wherein thelight transmitting layer is disposed in an optical path between theinput surface and the first group of lenticular elements; h) a lightcollimating element comprising a linear array of light redirectingfeatures oriented substantially parallel to the first axis with a secondpitch P2 wherein$\frac{0.9}{N + 0.5} < \frac{P\; 2}{P\; 1} < {\frac{1.1}{N + 0.5}\mspace{14mu}{or}\mspace{14mu}\frac{0.9}{N + 0.5}} < \frac{P\; 1}{P\; 2} < \frac{1.1}{N + 0.5}$where N is an integer.
 11. The optical element of claim 10 wherein thefirst light transmitting layer is disposed between the light collimatingelement and the first group of lenticular elements.
 12. The opticalelement of claim 10 wherein the first group of lenticular elements aredisposed between the light transmitting layer and the light collimatingelement.
 13. The optical element of claim 10 wherein the first group oflenticular elements and the light collimating element have a pitchcombination selected from the group P1 is between 180 μm and 195 μm andP2 is between 20 μm and 30 μm, P1 is between 415 μm and 435 μm and P2 isbetween 40 μm and 60 μm, and P1 is between 40 μm and 55 μm and P2 isbetween 350 μm and 365 μm.
 14. A light emitting device comprising: a) alight source; b) a first output surface; c) a light recyclingdirectional control element comprising; i. a linear array of lenticularelements formed in a first light transmitting material; ii. first lighttransmitting regions; iii. first light reflecting regions; iv. a firstgroup of lenticular elements oriented parallel to a first axis with afirst pitch P1; v. a light transmitting layer comprising the firstreflecting regions disposed in-between the first light transmittingregions wherein the light transmitting layer is disposed in an opticalpath between the input surface and the first group of lenticularelements; d) a light collimating element comprising a linear array oflight redirecting features oriented substantially parallel to the firstaxis with a second pitch P2 wherein$\frac{0.9}{N + 0.5} < \frac{P\; 2}{P\; 1} < {\frac{1.1}{N + 0.5}\mspace{14mu}{or}\mspace{14mu}\frac{0.9}{N + 0.5}} < \frac{P\; 1}{P\; 2} < \frac{1.1}{N + 0.5}$where N is an integer.
 15. The light emitting device of claim 14 whereinthe light recycling directional control element is disposed between thelight source and the light collimating element and the first reflectingregions are disposed to intersect the optical axes of the linear arrayof lenticular elements and the peak angle of luminance of the lightemitting from the light recycling directional control element is between20 degrees and 40 degrees from the normal to the first output surface.16. The light emitting device of claim 15 wherein the angle of peakluminance of the light emitted from the light emitting device is within5 degrees from the normal to the light transmitting layer.
 17. The lightemitting device of claim 15 wherein the light collimating elementcomprises a linear array of prisms with an apex angle between 80 degreesand 110 degrees and pitch between 40 μm and 60 μm.
 18. The lightemitting device of claim 14 wherein the linear array of lenticularelements and the light collimating element have a pitch combinationselected from the group P1 is between 180 μm and 195 μm and P2 isbetween 20 μm and 30 μm, P1 is between 415 μm and 435 μm and P2 isbetween 40 μm and 60 μm, and P1 is between 40 μm and 55 μm and P2 isbetween 350 μm and 365 μm.
 19. A display comprising a liquid crystalpanel and a backlight comprising the light emitting device of claim 14.